Process for dyeing keratin materials using a direct dye and an unsaturated heterocyclic salt, and composition comprising same

ABSTRACT

The present invention relates to a cosmetic process for treating keratin materials, in particular keratin fibers, preferably human keratin fibers such as the hair, using a) one or more direct dyes and b) one or more particular heterocyclic salts, to a composition comprising ingredients a) and b) and to a kit comprising a) and b).

The present invention relates to a cosmetic process for treating keratin materials, in particular keratin fibers, preferably human keratin fibers such as the hair, using a) one or more direct dyes and b) one or more particular heterocyclic salts, to a composition comprising ingredients a) and b) and to a kit comprising a) and b).

It is known practice to dye keratin fibers and in particular human hair with dye compositions containing oxidation dye precursors, which are generally known as oxidation bases, such as ortho- or para-phenylenediamines, ortho- or para-aminophenols and heterocyclic compounds. These oxidation bases are generally combined with couplers. These bases and couplers are colorless or weakly colored compounds, which, when combined with oxidizing products, may give rise to colored compounds by a process of oxidative condensation.

This type of oxidation dyeing makes it possible to obtain “permanent” colorings.

Moreover, it is known practice to dye keratin fibers and in particular human hair with dye compositions containing direct dyes. The standard dyes that are used are, in particular, dyes of the nitrobenzene, anthraquinone, nitropyridine, azo, xanthene, acridine, azine or triarylmethane type, or natural dyes. These dyes are colored or coloring molecules that have affinity for keratin fibers.

Compositions containing one or more direct dyes are applied to the keratin fibers for a time necessary to obtain the desired coloring, and are then rinsed out. The resulting colorings are particularly chromatic colorings, but are, however, temporary or semi-permanent since the nature of the interactions that bind the direct dyes to the keratin fiber and their desorption from the surface and/or the core of the fiber are responsible for their weak dyeing power and their poor persistence with respect to washing or perspiration.

Direct dyeing products notably make it possible to modify the natural color of the hair, or to cover white hairs. However, the intensity of the coloring obtained by using these products is occasionally judged as being too weak relative to the expectations of users on the day of application.

Moreover, the use of certain dyes, notably of anionic type, has a tendency to stain the scalp during the dyeing of the hair.

In addition, direct colorings have the drawback of fading out over time, in particular under the action of UV, inclement weather and successive shampooing.

The Applicant has now discovered, surprisingly, that a cosmetic process for treating keratin materials, in particular keratin fibers, notably human keratin fibers such as the hair, comprising the application to said keratin fibers of one or more direct dyes and one or more unsaturated heterocyclic salts, makes it possible notably to obtain better color build-up, and, furthermore, the colors are vivid and chromatic.

Thus, the invention relates to a process for dyeing keratin materials, in particular keratin fibers, preferably human keratin fibers such as the hair, using:

a) at least one direct dye, which is preferably anionic or neutral; and b) at least one unsaturated heterocyclic salt of formula (A) and also the optical, geometrical or tautomeric isomers thereof, and the solvates such as hydrates:

in which formula (A):

-   -   Het represents a 5- to 10-membered (preferentially 5- or         6-membered) cationic unsaturated aromatic heterocyclic group         comprising, besides the ammonium, from 1 to 3 heteroatoms,         preferentially 1 or 2 nitrogen or oxygen atoms, preferably 1         nitrogen atom, said heterocyclic group being optionally         substituted with one or more groups R′₁ or R₂;     -   R₁ and R′₁, which may be identical or different, represent a         linear or branched, saturated or unsaturated (C₁-C₁₂)         hydrocarbon-based group optionally substituted notably with one         or more groups chosen from hydroxyl, amino, (C₁-C₆)dialkylamino,         (C₁-C₆)alkylamino, carboxyl, carboxylate, carbamide,         (C₁-C₄)alkoxy, —SO₃H, sulfonate and phenyl; and     -   R² represents a hydroxyl radical, an amino radical, a linear or         branched, saturated or unsaturated (C₁-C₁₂) hydrocarbon-based         group optionally substituted notably with one or more groups         chosen from hydroxyl, amino, (C₁-C₆)dialkylamino,         (C₁-C₆)alkylamino, carboxyl, carboxylate, carbamide,         (C₁-C₄)alkoxy, —SO₃H, sulfonate and phenyl; and     -   Y⁻ represents an anionic counterion;         it being understood that:     -   when one of the hydrocarbon-based groups of R₁, R′₁ or R₂ is         substituted with a carboxylate or sulfonate group, then Y⁻ is         absent to ensure the electrical neutrality of the salt of         formula (A);     -   ingredients a) and b) are applied to said materials, together or         separately, i.e. sequentially; preferably, ingredients a) and b)         are applied together to said fibers.

Another subject of the invention is a cosmetic composition comprising ingredients a) and b) as defined previously. Another subject of the invention is the use of the composition for dyeing hair fibers, in particular human keratin fibers such as the hair.

Other subjects, characteristics, aspects and advantages of the invention will emerge even more clearly on reading the description and the examples that follow.

In the subsequent text, and unless otherwise indicated:

-   -   the dyes according to the invention contain one or more         chromophores, and these dyes are capable of absorbing light at a         wavelength labs particularly of between 400 and 700 nm         inclusive;     -   the “fluorescent” dyes according to the invention are dyes         containing at least one fluorescent chromophore, and these dyes         are capable of absorbing in the visible range at a wavelength         •_(abs) particularly inclusively between 400 and 800 nm and of         re-emitting in the visible range at a longer wavelength I_(em)         than that absorbed, inclusively between 400 and 800 nm. The         difference between the absorption and emission wavelengths, also         known as the Stoke's shift, is inclusively between 1 nm and 100         nm. More preferentially, fluorescent dyes are dyes that are         capable of absorbing at a wavelength •_(abs) inclusively between         420 and 550 nm and of re-emitting in the visible range at a         wavelength •_(em) inclusively between 470 and 600 nm;     -   an “alkylene” group represents a linear or branched C₁-C₁₀;         particularly C₁-C₆, more particularly C₁-C₂; acyclic         hydrocarbon-based divalent chain optionally substituted with one         or more groups, which may be identical or different, chosen         from i) hydroxyl, ii) (C₁-C₂)alkoxy, iii)         (poly)hydroxy(C₂-C₄)alkoxy(di)(C₁-C₂)(alkyl)amino, iv)         R^(a)—Z^(a)—C(Z^(b))—Z^(c)—, and v) R^(a)—Z^(a)—S(O)_(t)—Z^(c)—         with Z^(a), Z^(b), which may be identical or different,         representing an oxygen or sulfur atom or a group NR^(a′), Z^(c),         representing a bond, an oxygen or sulfur atom, or a group         NR^(a); R^(a), representing an alkali metal, a hydrogen atom, an         alkyl group or is absent if another part of the cationic         molecule and R^(a′) representing a hydrogen atom or an alkyl         group and t is equal to 1 or 2; preferably, the “alkylene” group         represents a group —(CH₂)_(P)— with p being an integer between 1         and 6, preferably between 1 and 4;     -   an “optionally substituted hydrocarbon-based” group represents a         hydrocarbon-based chain, particularly of C₁-C₈, optionally         comprising one or more conjugated or non-conjugated double bonds         p, in particular, the hydrocarbon-based chain is saturated; said         chain is optionally substituted with one or more groups, which         may be identical or different, chosen from i) hydroxyl, ii)         (C₁-C₂)alkoxy, iii)         (poly)hydroxy(C₂-C₄)alkoxy(di)(C₁-C₂)(alkyl)amino, iv)         R^(a)—Z^(a)—C(Z^(b))—Z^(c)—, and v) R^(a)—Z^(a)—S(O)_(t)—Z^(c)—         with Z^(a) and Z^(b), which may be identical or different,         representing an oxygen or sulfur atom, or a group NR^(a′),         Z^(c), representing a bond, an oxygen or sulfur atom, or a group         NR^(a); R^(a), representing an alkali metal, a hydrogen atom, an         alkyl group, or alternatively is absent if another part of the         cationic molecule and R^(a′) representing a hydrogen atom or an         alkyl group and t is equal to 1 or 2; more particularly, the         groups iv) are chosen from carboxylate —C(O)O or —C(O)OMetal         (metal=alkali metal), carboxyl —C(O)—OH, guanidino         H₂H—C(NH₂)—NH—, amidino H₂H—C(NH₂)—, (thio)ureo H₂N—C(O)—NH— and         H₂N—C(S)—NH—, aminocarbonyl —C(O)—NR^(a′) ₂ or aminothiocarbonyl         —C(S)—NR^(a′) ₂; carbamoyl R^(a′)—C(O)—NR^(a′)— or thiocarbamoyl         R^(a′)—C(S)—NRa′— with Ra′, which may be identical or different,         representing a hydrogen atom or a (C₁-C₄)alkyl group;     -   the “aryl” or “heteroaryl” radicals or the aryl or heteroaryl         part of a radical may be substituted with at least one         substituent borne by a carbon atom, chosen from:         -   a C₁-C₁₀ and preferably C₁-C₈ alkyl radical optionally             substituted with one or more radicals chosen from the             following radicals: hydroxyl, C₁-C₂ alkoxy,             (poly)hydroxy(C₂-C₄)alkoxy, acylamino, amino substituted             with two identical or different C₁-C₄ alkyl radicals             optionally bearing at least one hydroxyl group, or it being             possible for the two radicals to form, with the nitrogen             atom to which they are attached, a saturated or unsaturated             and optionally substituted 5- to 7-membered and preferably             5- or 6-membered heterocycle optionally comprising another             nitrogen or non-nitrogen heteroatom;         -   a halogen atom;         -   a hydroxyl group;         -   a C₁-C₂ alkoxy radical;         -   a C₂-C₄ (poly)hydroxyalkoxy radical;         -   an amino radical;         -   a 5- or 6-membered heterocycloalkyl radical;         -   an optionally cationic 5- or 6-membered heteroaryl radical,             preferentially imidazolium, optionally substituted with a             (C₁-C₄)alkyl radical, preferentially methyl;         -   an amino radical substituted with one or two identical or             different C₁-C₆ alkyl radicals, optionally bearing at least:         -   i) a hydroxyl group,         -   ii) an amino group optionally substituted with one or two             optionally substituted C₁-C₃ alkyl radicals, said alkyl             radicals possibly forming with the nitrogen atom to which             they are attached a saturated or unsaturated, optionally             substituted 5- to 7-membered heterocycle, optionally             comprising at least one other nitrogen or non-nitrogen             heteroatom,         -   iii) a quaternary ammonium group —N⁺R′R″R′″, M⁻ for which             R′, R″ and R′″, which may be identical or different,             represent a hydrogen atom or a C₁-C₄ alkyl group; and M⁻             represents the counterion of the corresponding organic or             mineral acid or of the corresponding halide;         -   iv) or an optionally cationic 5- or 6-membered heteroaryl             radical, preferentially imidazolium, optionally substituted             with a (C₁-C₄)alkyl radical, preferentially methyl;     -   an acylamino radical (—NR—C(O)—R′) in which the radical R is a         hydrogen atom or a C₁-C₄ alkyl radical optionally bearing at         least one hydroxyl group and the R′ radical is a C₁-C₂ alkyl         radical;     -   a carbamoyl radical ((R)₂N—C(O)—) in which the radicals R, which         may be identical or different, represent a hydrogen atom or a         C₁-C₄ alkyl radical optionally bearing at least one hydroxyl         group;     -   an alkylsulfonylamino radical (R′—S(O)₂—N(R)—) in which the         radical R represents a hydrogen atom or a C₁-C₄ alkyl radical         optionally bearing at least one hydroxyl group and the radical         R′ represents a C₁-C₄ alkyl radical or a phenyl radical; an         aminosulfonyl radical ((R)₂N—S(O)₂—) in which the radicals R,         which may be identical or different, represent a hydrogen atom         or a C₁-C₄ alkyl radical optionally bearing at least one         hydroxyl group;     -   a carboxylic radical in acid or salified (preferably with an         alkali metal or a substituted or unsubstituted ammonium) form;     -   a cyano group;     -   a nitro or nitroso group;     -   a polyhaloalkyl group, preferentially trifluoromethyl;         the cyclic or heterocyclic part of a non-aromatic radical may be         substituted with at least one substituent chosen from the         following groups:     -   hydroxyl;     -   C₁-C₄ alkoxy or C₂-C₄ (poly)hydroxyalkoxy;     -   C₁-C₄ alkyl;     -   alkylcarbonylamino (R—C(O)—N(R′)—) in which the radical R′ is a         hydrogen atom or a C₁-C₄ alkyl radical optionally bearing at         least one hydroxyl group, and the radical R is a C₁-C₂ alkyl         radical or an amino radical optionally substituted with one or         two C₁-C₄ alkyl groups, which may be identical or different,         optionally bearing at least one hydroxyl group, said alkyl         radicals possibly forming, with the nitrogen atom to which they         are attached a saturated or unsaturated, optionally substituted         5- to 7-membered heterocycle optionally comprising at least one         other nitrogen or non-nitrogen heteroatom;     -   alkylcarbonyloxy (R—C(O)—O—) in which the radical R is a C₁-C₄         alkyl radical or an amino group optionally substituted with one         or two identical or different C₁-C₄ alkyl groups optionally         bearing at least one hydroxyl group, said alkyl radicals         possibly forming with the nitrogen atom to which they are         attached a saturated or unsaturated, optionally substituted 5-         to 7-membered heterocycle, optionally comprising at least one         other nitrogen or non-nitrogen heteroatom;     -   alkoxycarbonyl (R-G-C(O)—) in which the radical R is a C₁-C₄         alkoxy radical, G is an oxygen atom or an amino group optionally         substituted with a C₁-C₄ alkyl group optionally bearing at least         one hydroxyl group, said alkyl radical possibly forming with the         nitrogen atom to which they are attached a saturated or         unsaturated, optionally substituted 5- to 7-membered         heterocycle, optionally comprising at least one other nitrogen         or non-nitrogen heteroatom;     -   a cyclic or heterocyclic radical, or a non-aromatic part of an         aryl or heteroaryl radical, may also be substituted with one or         more oxo groups;     -   a hydrocarbon-based chain is unsaturated when it includes one or         more double bonds and/or one or more triple bonds;     -   an “aryl” radical represents a fused or non-fused monocyclic or         polycyclic carbon-based group comprising from 6 to 22 carbon         atoms, and in which at least one ring is aromatic;         preferentially, the aryl radical is a phenyl, biphenyl,         naphthyl, indenyl, anthracenyl or tetrahydronaphthyl;     -   a “heteroaryl” group represents an optionally cationic, 5- to         22-membered, monocyclic or fused or non-fused polycyclic group,         comprising from 1 to 6 heteroatoms chosen from nitrogen, oxygen,         sulfur and selenium, at least one ring of which is aromatic;         preferentially, a heteroaryl radical is chosen from acridinyl,         benzimidazolyl, benzobistriazolyl, benzopyrazolyl,         benzopyridazinyl, benzoquinolyl, benzothiazolyl, benzotriazolyl,         benzoxazolyl, pyridinyl, tetrazolyl, dihydrothiazolyl,         imidazopyridyl, imidazolyl, indolyl, isoquinolyl,         naphthoimidazolyl, naphthoxazolyl, naphthopyrazolyl,         oxadiazolyl, oxazolyl, oxazolopyridyl, phenazinyl, phenoxazolyl,         pyrazinyl, pyrazolyl, pyrilyl, pyrazoyltriazyl, pyridyl,         pyridinoimidazolyl, pyrrolyl, quinolyl, tetrazolyl,         thiadiazolyl, thiazolyl, thiazolopyridinyl, thiazoylimidazolyl,         thiopyrylyl, triazolyl, xanthylyl and the ammonium salt thereof;     -   a “heterocyclic” group is a 5- to 22-membered, monocyclic or         fused or non-fused polycyclic radical that may contain one or         more aromatic or non-aromatic unsaturations, including from 1 to         6 heteroatoms chosen from nitrogen, oxygen and sulfur atoms;     -   a “heterocycloalkyl” radical is a saturated heterocyclic radical         such as morpholinyl, piperazinyl or piperidyl;     -   a “cationic heteroaryl” group is a heteroaryl radical as defined         previously that includes an endocyclic or exocyclic quaternized         cationic group,     -   when the cationic charge is endocyclic, it is included in the         electron delocalization via the mesomeric effect, for example it         is a pyridinium, imidazolium or indolinium group:

with R and R′ being a heteroaryl substituent as defined above and particularly a (hydroxy)(C₁-C₈)alkyl group such as methyl; when the charge is exocyclic, for example, it is an ammonium or phosphonium substituent R⁺ such as trimethylammonium, which is exterior to the heteroaryl such as pyridyl, indolyl, imidazolyl or naphthalimidyl in question;

with R a heteroaryl substituent as defined above and R⁺ an ammonium R_(a)R_(b)R_(c)N⁺—, phosphonium R_(a)R_(b)R_(c)P⁺— or ammonium R_(a)R_(b)R_(c)N⁺—(C₁-C₆)alkylamino group with R_(a), R_(b) and R_(c), which may be identical or different, representing a hydrogen atom or a (C₁-C₈)alkyl group such as methyl; a “cationic aryl group bearing an exocyclic charge” is an aryl ring whose quaternized cationic group is exterior to said ring; it is notably an ammonium or phosphonium R⁺ substituent, such as trimethylammonium, which is exterior to the aryl such as phenyl or naphthyl:

-   -   an “alkyl” group is a linear or branched C₁-C₁₀ and preferably         C₁-C₆ hydrocarbon-based radical;     -   an “alkenylene radical” is an unsaturated hydrocarbon-based         divalent radical as defined previously, which may contain from 1         to 4 conjugated or unconjugated double bonds —C═C—; the         alkenylene group particularly contains 1 or 2 unsaturations;     -   the term “optionally substituted” applied to the alkyl radical         implies that said alkyl radical may be substituted with one or         more radicals chosen from the following radicals: i)         hydroxyl, ii) C₁-C₄ alkoxy, iii) acylamino, iv) amino optionally         substituted with one or two identical or different C₁-C₄ alkyl         radicals, said alkyl radicals possibly forming with the nitrogen         atom that bears them a 5- to 7-membered heterocycle optionally         comprising another nitrogen or non-nitrogen heteroatom; v) or a         quaternary ammonium group —N⁺R′R″R″′, M⁻ for which R′, R″ and         R′″, which may be identical or different, represent a hydrogen         atom or a C₁-C₄ alkyl group, or alternatively —N⁺R′R″R″′ forms a         heteroaryl such as imidazolium optionally substituted with a         C₁-C₄ alkyl group, and M⁻ represents the counterion of the         organic or mineral acid or of the corresponding halide;     -   an “alkoxy radical” is an alkyl-oxy radical for which the alkyl         radical is a linear or branched C₁-C₁₀ and preferentially C₁-C₆         hydrocarbon-based radical;     -   when the alkoxy group is optionally substituted, this implies         that the alkyl group is optionally substituted as defined         hereinabove;     -   the “tone depth” is the unit known to hairstyling professionals,         and published in the book “Science des traitements capillaires         [Science of hair treatment]” by Charles ZVIAK 1988, edited by         Masson, pages 215 and 278; the tone depths range from 1 (black)         to 10 (very light blond), one unit corresponding to one tone,         the higher the figure, the lighter the shade;     -   a “dark” keratin fiber is a keratin fiber whose lightness L*         measured in the CIE L*a*b* system is less than or equal to 45         and preferably less than or equal to 40, given that L*=0 is         equivalent to black and L*=100 is equivalent to white;     -   “naturally or artificially dark hair” means hair whose tone         depth is less than or equal to 6 (dark blond) and preferably         less than or equal to 4 (chestnut-brown). Artificially dyed hair         is hair whose color has been modified by a dye treatment, for         example dyeing with direct dyes or oxidation dyes;     -   the term “anionic counterion” refers to an anion or an anionic         group derived from an organic or mineral acid salt which         counterbalances the cationic charge of the cationic salt; the         anionic counterion, derived from the organic or mineral acid         salt, ensures the electrical neutrality of the molecule; it is         thus understood that when the anion comprises several anionic         charges, then the same anion may serve for the electrical         neutrality;     -   moreover, the addition salts that may be used in the context of         the invention are notably chosen from addition salts with a         cosmetically acceptable base such as the basifying agents as         defined below, for instance alkali metal hydroxides such as         sodium hydroxide, potassium hydroxide, aqueous ammonia, amines         or alkanolamines;     -   the expression “at least one” is equivalent to “one or more”;     -   the limits of a range of values are included in that range,         notably in the expressions “between . . . and . . . ” and         “ranging from . . . to . . . ”; and     -   the expression “inclusive” for a range of concentrations means         that the limits of the range are included in the defined         interval.

a) Direct Dye:

The term “direct dye” means natural and/or synthetic dyes, other than oxidation dyes. These are dyes that will spread superficially on the fiber. They may be ionic or nonionic, i.e. anionic, cationic, neutral or nonionic. Direct dyes may be of the same types of ionicity or else as mixtures. According to a particular embodiment of the invention, the direct dyes a) are neutral, cationic or anionic direct dyes chosen from: acridines; acridones; anthranthrones; anthrapyrimidines; anthraquinones; azines; (poly)azos or azos, hydrazono or hydrazones, in particular arylhydrazones; azomethines; benzanthrones; benzimidazoles; benzimidazolones; benzindoles; benzoxazoles; benzopyrans; benzothiazoles; benzoquinones; bis-isoindolines; carboxanilides; coumarins; cyanines, such as (di)azacarbocyanines, (di)azahemicyanines, hemicyanines or tetraazacarbocyanines; (di)azines; bis-azines; (di)oxazines; (di)thiazines; (di)phenylamines; (di)phenylmethanes; (di)ketopyrrolopyrroles; flavonoids, such as flavanthrones and flavones; fluorindines; formazans; indamines; indanthrones; indigoids, thioindigoids and pseudoindigoids; indophenols; indoanilines; isoindolines; isoindolinones; isoviolanthrones; lactones; (poly)methines, such as dimethines of stilbene or styryl types; naphthalimides; naphthanilides; naphtholactams; naphthoquinones; nitro, notably nitro(hetero)aromatics; oxadiazoles; oxazines; perilones; perinones; perylenes; phenazines; phenoxazines; phenothiazines; phthalocyanines; polyenes/carotenoids; porphyrins; pyranthrones; pyrazolanthrones; pyrazolones; pyrimidinoanthrones; pyronines; quinacridones; quinolines; quinophthalones; squaranes; tetrazolines; thiazines; thiopyronines; triarylmethanes or xanthenes and natural direct dyes; more preferentially, the direct dyes a) of the invention are chosen from anthraquinones, (poly)azos, azomethines and stilbenes.

The direct dyes a) are in particular chosen from nitrobenzene direct dyes, which are neutral, cationic (or basic dyes) or anionic (or acid dyes), azo direct dyes, which are neutral, cationic (or basic dyes) or anionic (or acid dyes), tetraazapentamethine dyes, which are neutral, cationic (or basic dyes) or anionic (or acid dyes), quinone dyes, which are cationic (or basic dyes) or anionic (or acid dyes) and in particular anthraquinones, which are neutral, cationic (or basic dyes) or anionic (or acid dyes), azine direct dyes, which are neutral, cationic (or basic dyes) or anionic (or acid dyes), triarylmethane direct dyes, which are neutral, cationic (or basic dyes) or anionic (or acid dyes), azomethine direct dyes, which are neutral, cationic (or basic dyes) or anionic (or acid dyes), and natural direct dyes.

More particularly, the direct dyes a) are chosen from azo direct dyes; (poly)methine dyes such as cyanines, hemicyanines and styryl dyes; carbonyl dyes; azine dyes; nitro(hetero)aryl dyes; tri(hetero)arylmethane dyes; porphyrin dyes; phthalocyanine dyes, and natural direct dyes, alone or as mixtures.

The neutral, anionic or cationic direct dyes according to the invention are preferably chosen from the following dyes: acridines; acridones; anthranthrones; anthrapyrimidines; anthraquinones; azines; (poly)azos, hydrazono or hydrazones, in particular arylhydrazones; azomethines; benzanthrones; benzimidazoles; benzimidazolones; benzindoles; benzoxazoles; benzopyrans; benzothiazoles; benzoquinones; bisazines; bis-isoindolines; carboxanilides; coumarins; cyanines, such as azacarbocyanines, diazacarbocyanines, diazahemicyanines, hemicyanines or tetraazacarbocyanines; diazines; diketopyrrolopyrroles; dioxazines; diphenylamines; diphenylmethanes; dithiazines; flavonoids, such as flavanthrones and flavones; fluorindines; formazans; indamines; indanthrones; indigoids and pseudoindigoids; indophenols; indoanilines; isoindolines; isoindolinones; isoviolanthrones; lactones; (poly)methines, such as dimethines of stilbene or styryl types; naphthalimides; naphthanilides; naphtholactams; naphthoquinones; nitro, notably nitro(hetero)aromatics; oxadiazoles; oxazines; perilones; perinones; perylenes; phenazines; phenoxazines; phenothiazines; phthalocyanines; polyenes/carotenoids; porphyrins; pyranthrones; pyrazolanthrones; pyrazolones; pyrimidinoanthrones; pyronines; quinacridones; quinolines; quinophthalones; squaranes; tetrazole; thiazines; thioindigos; thiopyronines; triarylmethanes or xanthenes.

Preferentially, the direct dye(s) a) are neutral direct dyes; preferably chosen from the hydrazono dyes of formulae (IIIa) and (III′a), the azo and styryl dyes (IVa), the diazo and distyryl dyes (IV′a) and (VI″a), the anthraquinone dyes (Va) and the azomethine dyes (VIa) and (VI′a) below:

in which formulae (IIIa), (III′a), (IVa), (IV′a), (IV″a), (Va), (VIa) and (VI′a):

-   -   Ar represents an aryl radical, such as phenyl or naphthyl,         substituted with at least one electron-donating group such as i)         optionally substituted (C₁-C₈)alkyl, ii) optionally substituted         (C₁-C₈)alkoxy, iii) amino, iv) (di)(C₁-C₈)(alkyl)amino         optionally substituted on the alkyl group(s) with a hydroxyl         group, v) aryl(C₁-C₈)alkylamino, vi) optionally substituted         N—(C₁-C₈)alkyl-N-aryl(C₁-C₈)alkylamino or, as a variant, Ar         represents a julolidine group;     -   Ar′ represents an optionally substituted divalent         (hetero)arylene group such as phenylene, particularly         para-phenylene, or naphthalene, which is optionally substituted,         preferably with one or more (C₁-C₈)alkyl, hydroxyl or         (C₁-C₈)alkoxy groups;     -   Ar″ represents a (hetero)aryl radical, which is optionally         substituted, preferably with at least i) an electron-withdrawing         group such as nitro, nitroso, —C(X)—X′—R′ or ii) a         (di)(C₁-C₆)(alkyl)amino group, iii) hydroxyl, iv) (C₁-C₆)alkoxy;         (hetero)aryl is particularly chosen from imidazolyl, triazolyl,         indolyl or pyridyl or phenyl optionally substituted with at         least one group chosen from nitro, nitroso and amino, preferably         substituted in the position para to the phenyl group;     -   X, X′ and X″, which may be identical or different, represent an         oxygen or sulfur atom, or a group NR″, preferably an oxygen         atom;     -   R₁, R², R³ and R⁴, which may be identical or different,         represent a hydrogen or halogen atom, or a group chosen from         hydroxyl, thiol, (C₁-C₄)alkyl, (C₁-C₄)alkoxy,         (di)(C₁-C₄)(alkyl)amino, nitro and nitroso;     -   R′ and R″ represent a (C₁-C₄)alkyl group;     -   R^(a) and R^(b), which may be identical or different, represent         a hydrogen atom or a (C₁-C₈)alkyl group, which is optionally         substituted, preferably with a hydroxyl group;         or, as a variant, the substituent R^(a) with a substituent of         Ar″ and/or R^(b) with a substituent of Ar and/or R^(a) with         R^(b) form, together with the atoms that bear them, a         (hetero)cycloalkyl;         particularly, R^(a) and R^(b) represent a hydrogen atom or a         (C₁-C₄)alkyl group, which is optionally substituted with a         hydroxyl group;     -   T and T′, which may be identical or different, represent a group         C(R^(a)) or N, preferably N; and     -   L represents a divalent group -ALK-, —C(X)-ALK-, -ALK—C(X)— or         —C(X)-ALK-C(X′)— with ALK representing a linear or branched         (C₁-C₆)alkylene group, such as methylene and X and X′, as         defined previously,         R²², R²³, R²⁴, R²⁵, R²⁶ and R²⁷, which may be identical or         different, represent a hydrogen or halogen atom, or a group         chosen from:     -   (C₁-C₆)alkyl;     -   hydroxyl, mercapto;     -   (C₁-C₆)alkoxy, (C₁-C₆)alkylthio;     -   aryloxy or arylthio;     -   aryl(C₁-C₆)(alkyl)amino;     -   (di)(C₁-C₆)(alkyl)amino;     -   (di)(hydroxy(C₁-C₆)alkyl)amino;     -   Z′ represents a hydrogen atom or a group NR₂₈R₂₉ with R₂₈ and         R₂₉, which may be identical or different, representing a         hydrogen atom or a group chosen from:     -   (C₁-C₆)alkyl;     -   polyhydroxy(C₁-C₆)alkyl such as hydroxyethyl;     -   aryl optionally substituted with one or more groups,         particularly i) (C₁-C₆)alkyl; iii) R^(o)—C(X)—X′—,         R^(o)—X′—C(X)—, R^(o)—X′—C(X)—X″— with R^(o) representing a         (C₁-C₆)alkyl group, a sulfonate;     -   cycloalkyl; notably cyclohexyl;     -   Z represents a group chosen from hydroxyl and NR′₂₈R′₂₉ with         R′₂₈ and R′₂₉, which may be identical or different, representing         the same atoms or groups as R₂₈ and R₂₉ as defined previously.

According to one embodiment, the direct dyes a) are of formula (IV″a), particularly of formula (IV′″a), and also the optical, geometrical or tautomeric isomers thereof, the organic or mineral acid or base salts thereof, and solvates thereof such as hydrates:

in which formula (IV″a):

-   -   R₁ and R₃, which may be identical or different, preferably         identical, represent a hydrogen atom, a (C₁-C₄)alkyl group such         as methyl or a sugar such as glucosyl, preferably a hydrogen         atom;     -   R₂ and R₄, which may be identical or different, preferably         identical, represent a hydrogen atom, a (C₁-C₄)alkyl or         (C₁-C₄)alkoxy group or an —O-sugar group such as —O-glucosyl,         preferably (C₁-C₄)alkoxy; such as methoxy;     -   X, which may be identical or different, preferably identical,         represents an oxygen or sulfur atom or N—R with R representing a         hydrogen atom, preferably an oxygen atom;     -   ALK represents a (C₁-C₄) alkylene group such as methylene or         ethylene, preferably methylene.

The dyes of formula (IV″a) may be derived from curcumin, demethoxycurcumin and bis-demethoxycurcumin.

Preferentially, the direct dyes a) of the invention are neutral direct dyes chosen from the azo dyes (IVb), the distyryl dyes (VI″b), the anthraquinone dyes (Vb) and the azomethine dyes (VIb):

and also the organic or mineral acid or base salts thereof, the optical or geometrical isomers ‘ ’ thereof, and the solvates thereof such as hydrates, preferably chosen from (E) and (G).

According to another particular embodiment of the invention, the direct dyes a) are chosen from cationic direct dyes or dyes commonly referred to as “basic” direct dyes or “basic dyes” on account of their affinity for acidic substances.

For the cationic azo dyes, mention may be made particularly of the cationic dyes described in Kirk-Othmer's Encyclopedia of Chemical Technology, “Dyes, Azo”, J. Wiley & Sons, updated on 19 Apr. 2010.

Among the azo dyes that may be used according to the invention, mention may be made of the cationic azo dyes described in patent applications WO 95/15144, WO 95/01772 and EP-714954. According to a particular embodiment of the invention, the direct dye(s) are chosen from cationic dyes known as “basic dyes”.

Among the azo dyes described in the Colour Index International 3rd edition, mention may be made notably of the following compounds: Basic Red 22; Basic Red 76; Basic Yellow 57; Basic Brown 16; Basic Brown 17.

Among the cationic quinone dyes, those mentioned in the abovementioned Colour Index International are suitable and, among these, mention may be made, inter alia, of the following dyes: Basic Blue 22; Basic Blue 99.

Among the azine dyes that are suitable for use, mention may be made of those listed in the Colour Index International, for example the following dyes: Basic Blue 17, Basic Red 2.

Among the cationic triarylmethane dyes that may be used according to the invention, mention may be made, in addition to those listed in the Colour Index, of the following dyes: Basic Green 1, Basic Violet 3, Basic Violet 14, Basic Blue 7 and Basic Blue 26.

Mention may also be made of the direct dyes described in U.S. Pat. No. 5,888,252, EP 1 133 975, WO 03/029 359, EP 860 636, WO 95/01772, WO 95/15144 and EP 714 954. Mention may also be made of those listed in the encyclopedia “The Chemistry of Synthetic Dyes” by K. Venkataraman, 1952, Academic Press, vol. 1 to 7, in the “Kirk-Othmer Encyclopedia of Chemical Technology”, in the chapter “Dyes and Dye Intermediates”, 1993, Wiley and Sons, and in various chapters of “Ullmann's Encyclopedia of Industrial Chemistry”, 7th edition, Wiley and Sons.

Preferably, the direct dyes are chosen from those resulting from dyes of azo and hydrazono type.

According to a particular embodiment, the direct dyes are cationic azo dyes, described in EP 850 636, FR 2 788 433, EP 920 856, WO 99/48465, FR 2 757 385, EP 850 637, EP 918 053, WO 97/44004, FR 2 570 946, FR 2 285 851, DE 2 538 363, FR 2 189 006, FR 1 560 664, FR 1 540 423, FR 1 567 219, FR 1 516 943, FR 1 221 122, DE 4 220 388, DE 4 137 005, WO 01/66646, U.S. Pat. No. 5,708,151, WO 95/01772, WO 515 144, GB 1 195 386, U.S. Pat. Nos. 3,524,842, 5,879,413, EP 1 062 940, EP 1 133 976, GB 738 585, DE 2 527 638, FR 2 275 462, GB 1974-27645, Acta Histochem. (1978), 61(1), 48-52; Tsitologiya (1968), 10(3), 403-5; Zh. Obshch. Khim. (1970), 40(1), 195-202; Ann. Chim. (Rome) (1975), 65(5-6), 305-14; Journal of the Chinese Chemical Society (Taipei) (1998), 45(1), 209-211; Rev. Roum. Chim. (1988), 33(4), 377-83; Text. Res. J. (1984), 54(2), 105-7; Chim. Ind. (Milan) (1974), 56(9), 600-3; Khim. Tekhnol. (1979), 22(5), 548-53; Ger. Monatsh. Chem. (1975), 106(3), 643-8; MRL Bull. Res. Dev. (1992), 6(2), 21-7; Lihua Jianyan, Huaxue Fence (1993), 29(4), 233-4; Dyes Pigm. (1992), 19(1), 69-79; Dyes Pigm. (1989), 11(3), 163-72.

Preferably, the direct dye(s) of the invention comprise a quaternary ammonium group; more preferentially, the cationic charge is endocyclic.

These cationic radicals are, for example, a cationic radical:

-   -   bearing an exocyclic (di/tri)(C₁-C₈)alkylammonium charge, or     -   bearing an endocyclic charge, such as comprising a cationic         heteroaryl group chosen from: acridinium, benzimidazolium,         benzobistriazolium, benzopyrazolium, benzopyridazinium,         benzoquinolium, benzothiazolium, benzotriazolium, benzoxazolium,         bipyridinium, bis-tetrazolium, dihydrothiazolium,         imidazopyridinium, imidazolium, indolium, isoquinolium,         naphthoimidazolium, naphthoxazolium, naphthopyrazolium,         oxadiazolium, oxazolium, oxazolopyridinium, oxonium,         phenazinium, phenooxazolium, pyrazinium, pyrazolium,         pyrazoyltriazolium, pyridinium, pyridinoimidazolium, pyrrolium,         pyrylium, quinolium, tetrazolium, thiadiazolium, thiazolium,         thiazolopyridinium, thiazoylimidazolium, thiopyrylium,         triazolium or xanthylium.

Mention may be made of the hydrazono cationic dyes of formulae (IIb) and (IIIb) and the azo cationic dyes of formulae (IVb) and (Vb) below:

in which formulae (IIb) to (Vb):

-   -   Het⁺ represents a cationic heteroaryl radical, preferentially         bearing an endocyclic cationic charge, such as imidazolium,         indolium or pyridinium, which is optionally substituted,         preferentially with at least one (C₁-C₈) alkyl group such as         methyl;     -   Ar⁺ represents an aryl radical, such as phenyl or naphthyl,         bearing an exocyclic cationic charge, preferentially ammonium,         particularly tri(C₁-C₈)alkylammonium, such as trimethylammonium;     -   Ar represents an aryl group, notably phenyl, which is optionally         substituted, preferentially with one or more electron-donating         groups such as i) optionally substituted (C₁-C₈)alkyl, ii)         optionally substituted (C₁-C₈)alkoxy, iii)         (di)(C₁-C₈)(alkyl)amino optionally substituted on the alkyl         group(s) with a hydroxyl group, iv) aryl(C₁-C₈)alkylamino, v)         optionally substituted N—(C₁-C₈)alkyl-N-aryl(C₁-C₈)alkylamino or         alternatively Ar represents a julolidine group;     -   Ar″ represents an optionally substituted (hetero)aryl group,         such as phenyl or pyrazolyl, which are optionally substituted,         preferentially by one or more (C₁-C₈)alkyl, hydroxyl,         (di)(C₁-C₈)(alkyl)amino, (C₁-C₈)alkoxy or phenyl groups; —R_(a)         and R_(b), which may be identical or different, represent a         hydrogen atom or a (C₁-C₈)alkyl group, which is optionally         substituted, preferentially with a hydroxyl group;     -   or else the substituent R_(a) with a substituent of Het⁺ and/or         R_(b) with a substituent of Ar form, together with the atoms         that bear them, a (hetero)cycloalkyl; in particular, R_(a) and         R_(b) represent a hydrogen atom or a (C₁-C₄)alkyl group         optionally substituted with a hydroxyl group;     -   Q⁻ represents an anionic counterion such as a halide, an alkyl         sulfate or an alkylsulfonate.

In particular, mention may be made of the azo and hydrazono direct dyes bearing an endocyclic cationic charge of formulae (Mb) to (Vb) as defined previously. More particularly, the cationic direct dyes of formulae (IIb) to (Vb) bearing an endocyclic cationic charge described in patent applications WO 95/15144, WO 95/01772 and EP 714 954. Preferentially the following direct dyes:

in which formulae (II-1) and (IV-1):

-   -   R₁ represents a (C₁-C₄)alkyl group such as methyl;     -   R₂ and R₃, which may be identical or different, represent a         hydrogen atom or a (C₁-C₄)alkyl group, such as methyl; and     -   R₄ represents a hydrogen atom or an electron-donating group such         as optionally substituted (C₁-C₈)alkyl, optionally substituted         (C₁-C₈)alkoxy, or (di)(C₁-C₈)(alkyl)amino optionally substituted         on the alkyl group(s) with a hydroxyl group; particularly, R₄ is         a hydrogen atom,     -   Z represents a CH group or a nitrogen atom, preferentially CH,     -   Q⁻ is an anionic counterion as defined above, in particular a         halide, such as chloride, or an alkyl sulfate, such as methyl         sulfate or mesityl.

Particularly, the dyes of formulae (II-1) and (IV-1) are chosen from Basic Red 51, Basic Yellow 87 and Basic Orange 31 or derivatives thereof:

with Q′ being an anionic counterion as defined previously, in particular a halide, such as chloride, or an alkyl sulfate, such as methyl sulfate or mesityl.

According to a particular embodiment of the invention, the direct dyes are fluorescent, i.e. they contain at least one fluorescent chromophore as defined previously.

Fluorescent dyes that may be mentioned include neutral, anionic or cationic dyes chosen from the following dyes: acridines, acridones, benzanthrones, benzimidazoles, benzimidazolones, benzindoles, benzoxazoles, benzopyrans, benzothiazoles, coumarins, difluoro{2-[(2H-pyrrol-2-ylidene-kN)methyl]-1H-pyrrolato-kN}borons (BODIPY®), diketopyrrolopyrroles, fluorindines, (poly)methines (in particular cyanines and styryls/hemicyanines), naphthalimides, naphthanilides, naphthylamines (such as dansyls), oxadiazoles, oxazines, perilones, perinones, perylenes, polyenes/carotenoids, squaranes, stilbenes, xanthenes.

Mention may also be made of the fluorescent dyes described in the documents EP 1 133 975, WO 03/029 359, EP 860 636, WO 95/01772, WO 95/15144 and EP 714 954 and those listed in the encyclopedia “The Chemistry of Synthetic Dyes” by K. Venkataraman, 1952, Academic Press, vol. 1 to 7, in the “Kirk-Othmer Encyclopedia of Chemical Technology”, in the chapter “Dyes and Dye Intermediates”, 1993, Wiley and Sons, and in various chapters of “Ullmann's Encyclopedia of Industrial Chemistry”, 7th edition, Wiley and Sons, and in the handbook—“A Guide to Fluorescent Probes and Labeling Technologies”, 10th Ed., Molecular Probes/Invitrogen—Oregon 2005, circulated on the Internet or in the preceding printed editions.

According to a preferred variant of the invention, the fluorescent dye(s) are cationic polymethines and comprise at least one quaternary ammonium radical, such as those of formula (Vb) below:

in which formula (Vb):

-   -   W⁺ represents a cationic heterocyclic or heteroaryl group,         particularly comprising a quaternary ammonium optionally         substituted with one or more (C₁-C₈)alkyl groups, optionally         substituted notably with one or more hydroxyl groups;     -   Ar representing an aryl group such as phenyl or naphthyl,         optionally substituted preferentially with i) one or more         halogen atoms such as chlorine or fluorine; ii) one or more         groups (C₁-C₈)alkyl, preferably of C₁-C₄ such as methyl; iii)         one or more hydroxyl groups; iv) one or more (C₁-C₈)alkoxy         groups such as methoxy; v) one or more hydroxy(C₁-C₈)alkyl         groups such as hydroxyethyl, vi) one or more amino groups or         (di)(C₁-C₈)alkylamino, preferably with the C₁-C₄ alkyl part         optionally substituted with one or more hydroxyl groups, such as         (di)hydroxyethylamino, vii) with one or more acylamino         groups; viii) one or more heterocycloalkyl groups such as         piperazinyl, piperidyl or 5- or 6-membered heteroaryl such as         pyrrolidinyl, pyridyl and imidazolinyl;     -   m′ represents an integer between 1 and 4 inclusive; in         particular, m is 1 or 2; more preferentially 1;     -   R_(c) and R_(d), which may be identical or different, represent         a hydrogen atom or an optionally substituted (C₁-C₈)alkyl group,         preferentially of C₁-C₄, or alternatively R_(c) contiguous with         W⁺ and/or R_(d) contiguous with Ar form, with the atoms that         bear them, a (hetero)cycloalkyl; particularly, R_(c) is         contiguous with W⁺ and they form a (hetero)cycloalkyl such as         cyclohexyl;     -   Q⁻ is an anionic counterion as defined previously.

According to a preferred embodiment of the invention, the direct dyes a) are chosen from anionic direct dyes or dyes commonly referred to as “acidic” direct dyes on account of their affinity for alkaline substances. The term “anionic direct dye” means any direct dye including in its structure at least one CO₂R or SO₃R substituent with R denoting a hydrogen atom or a cation originating from a metal or an amine, or an ammonium ion. The anionic dyes may be chosen from direct nitro acid dyes, azo acid dyes, azine acid dyes, triarylmethane acid dyes, indoamine acid dyes, anthraquinone acid dyes, indigoid dyes and natural acid dyes; preferably, the direct dyes a) are acidic anthraquinone dyes.

As acid dyes according to the invention, mention may be made of the dyes of formulae (III), (III′), (IV), (IV′), (V), (V′), (VI), (VI′), (VII), (VIII), (IX) and (X) below:

a) the diaryl anionic azo dyes of formula (III) or (III′):

in which formulae (III) and (III′):

-   -   R₇, R₈, R₉, R₁₀, R′₇, R′₈, R′₉ and R′₁₀, which may be identical         or different, represent a hydrogen atom or a group chosen from:     -   (C₁-C₆)alkyl;     -   (C₁-C₆)alkoxy, (C₁-C₆)alkylthio;     -   hydroxyl, mercapto;     -   nitro, nitroso;     -   R^(o)—C(X)—X′—, R^(o)—X′—C(X)—, R^(o)—X′—C(X)—X″— with R^(o)         representing a hydrogen atom or a (C₁-C₆)alkyl or aryl group         such as phenyl; X, X′ and X″, which may be identical or         different, representing an oxygen or sulfur atom, or NR with R         representing a hydrogen atom or a (C₁-C₆)alkyl group;     -   (O)₂S(O⁻)—, M⁺ with M⁺ representing a hydrogen atom or a         cationic counterion;     -   (O)CO⁻—, M⁺ with M⁺ as defined previously;     -   R″—S(O)₂—, with R″ representing a hydrogen atom, an alkyl group,         or an aryl, (di)(C₁-C₆)(alkyl)amino or aryl(C₁-C₆)(alkyl)amino         group; preferentially a phenylamino or phenyl group;     -   R″′—S(O)₂—X′— with R″′ representing a (C₁-C₆)alkyl group or an         aryl group which is optionally substituted, X′ as defined         previously;     -   (di)(C₁-C₆)(alkyl)amino;     -   aryl(C₁-C₆)(alkyl)amino optionally substituted with one or more         groups chosen from i) nitro; ii) nitroso; iii) (O)₂S(O⁻)—, M⁺         and iv) (C₁-C₆)alkoxy with M⁺ as defined previously;     -   optionally substituted heteroaryl; preferentially a         benzothiazolyl group;     -   cycloalkyl; notably cyclohexyl;     -   Ar-N═N— with Ar representing an optionally substituted aryl         group; preferentially a phenyl optionally substituted with one         or more alkyl, (O)₂S(O⁻)—, M⁺ or phenylamino groups;     -   or alternatively two contiguous groups R₇ with R₈ or R₈ with R₉         or R₉ with R₁₀ together form a fused benzo group A′; and R′₇         with R′₈ or R′₈ with R′₉ or R′₉ with R′₁₀ together form a fused         benzo group B′; with A′ and B′ optionally substituted with one         or more groups chosen from i) nitro; ii) nitroso; iii)         (O)₂S(O⁻)—, M⁺; iv) hydroxyl; v) mercapto; vi)         (di)(alkyl)amino; vii) R^(o)—C(X)—X′—; viii) R^(o)—X′—C(X)—; ix)         R^(o)—X′—C(X)—X″—; x) Ar-N═N— and xi) optionally substituted         aryl(C₁-C₆)(alkyl)amino; with M⁺, R^(o), X, X′, X″ and Ar as         defined previously;     -   W represents a sigma bond σ, an oxygen or sulfur atom, or a         divalent radical i) —NR— with R as defined previously, or ii)         methylene —C(R_(a))(R_(b))— with R_(a) and R_(b), together which         may be identical or different, representing a hydrogen atom or         an aryl group, or alternatively R_(a) and R_(b) form, together         with the carbon atom that bears them, a spiro cycloalkyl;         preferentially, W represents a sulfur atom or R_(a) and R_(b)         together form a cyclohexyl;     -   it being understood that formulae (III) and (III′) comprise at         least one sulfonate radical (O)₂S(O)—, M⁺ or one carboxylate         radical (O)CO⁻—, M⁺ on one of the rings A, A′, B, B′ or C;         preferentially sodium sulfonate.

As examples of dyes of formula (III), mention may be made of: Acid Red 1, Acid Red 4, Acid Red 13, Acid Red 14, Acid Red 18, Acid Red 27, Acid Red 28, Acid Red 32, Acid Red 33, Acid Red 35, Acid Red 37, Acid Red 40, Acid Red 41, Acid Red 42, Acid Red 44, Pigment red 57, Acid Red 68, Acid Red 73, Acid Red 135, Acid Red 138, Acid Red 184, Food Red 1, Food Red 13, Acid Orange 6, Acid Orange 7, Acid Orange 10, Acid Orange 19, Acid Orange 20, Acid Orange 24, Yellow 6, Acid Yellow 9, Acid Yellow 36, Acid Yellow 199, Food Yellow 3, Acid Violet 7, Acid Violet 14, Acid Blue 113, Acid Blue 117, Acid Black 1, Acid Brown 4, Acid Brown 20, Acid Black 26, Acid Black 52, Food Black 1, Food Black 2, Food yellow 3 or Sunset Yellow;

and as examples of dyes of formula (III′), mention may be made of: Acid Red 111, Acid Red 134, Acid Yellow 38;

-   -   b) the pyrazolone anionic azo dyes of formulae (IV) and (IV′):

in which formulae (IV) and (IV′):

R₁₁, R₁₂ and R₁₃, which may be identical or different, represent a hydrogen or halogen atom, a (C₁-C₆)alkyl group or —(O)₂S(O⁻), M⁺ with M⁺ as defined previously;

R₁₄ represents a hydrogen atom, a (C₁-C₆)alkyl group or a —C(O)O⁻, M⁺ group with M⁺ as defined previously;

R₁₅ represents a hydrogen atom;

R₁₆ represents an oxo group, in which case R′₁₆ is absent, or alternatively R₁₅ with R₁₆ together form a double bond;

R₁₇ and R₁₈, which may be identical or different, represent a hydrogen atom or a group chosen from:

-   -   (O)₂S(O⁻)—, M⁺ with M⁺ as defined previously;     -   Ar-O—S(O)₂— with Ar representing an optionally substituted aryl         group, preferentially a phenyl optionally substituted with one         or more alkyl groups;

R₁₉ and R₂₀ together form either a double bond, or a benzo group D′, which is optionally substituted;

R′₁₆, R′₁₉ and R′₂₀, which may be identical or different, represent a hydrogen atom or a (C₁-C₆)alkyl or hydroxyl group;

R₂₁ represents a hydrogen atom or a (C₁-C₆)alkyl or (C₁-C₆)alkoxy group;

R_(a) and R_(b), which may be identical or different, are as defined previously; preferentially, R_(a) represents a hydrogen atom and R_(b) represents an aryl group such as phenyl;

Y represents either a hydroxyl group or an oxo group;

represents a single bond when Y is an oxo group; and represents a double bond when Y represents a hydroxyl group;

it being understood that formulae (IV) and (IV′) comprise at least one sulfonate radical (O)₂S(O)—, M⁺ or one carboxylate radical C(O)O—, M⁺ on one of the rings D or E; preferentially sodium sulfonate;

As examples of dyes of formula (IV), mention may be made of: Acid Red 195, Acid Yellow 23, Acid Yellow 27, Acid Yellow 76, and as examples of dyes of formula (IV′), mention may be made of: Acid Yellow 17;

c) the anthraquinone dyes of formulae (V) and (V′):

in which formulae (V) and (V′):

R₂₂, R₂₃, R₂₄, R₂₅, R₂₆ and R₂₇, which may be identical or different, represent a hydrogen or halogen atom, or a group chosen from:

-   -   (C₁-C₆)alkyl;     -   hydroxyl, mercapto;     -   (C₁-C₆)alkoxy, (C₁-C₆)alkylthio;     -   optionally substituted aryloxy or arylthio, preferentially         substituted with one or more groups chosen from alkyl and         (O)₂S(O⁻)—, M⁺ with M⁺ as defined previously;     -   aryl(C₁-C₆)(alkyl)amino optionally substituted with one or more         groups chosen from alkyl and (O)₂S(O⁻)—, M⁺ with M⁺ as defined         previously;     -   (di)(C₁-C₆)(alkyl)amino;     -   (di)(hydroxy(C₁-C₆)alkyl)amino;     -   (O)₂S(O⁻)—, M⁺ with M⁺ as defined previously;

Z′ represents a hydrogen atom or a group NR₂₈R₂₉ with R₂₈ and R₂₉, which may be identical or different, representing a hydrogen atom or a group chosen from:

-   -   (C₁-C₆)alkyl;     -   polyhydroxy(C₁-C₆)alkyl such as hydroxyethyl;     -   aryl optionally substituted with one or more groups,         particularly i) (C₁-C₆)alkyl such as methyl, n-dodecyl,         n-butyl; ii) (O)₂S(O⁻)—, M⁺ with M⁺ as defined previously; iii)         R^(o)—C(X)—X′—, R^(o)—X′—C(X)—, R^(o)—X′—C(X)—X″— with R^(o), X,         X′ and X″ as defined previously, preferentially R^(o) represents         a (C₁-C₆)alkyl group;     -   cycloalkyl; notably cyclohexyl;

Z represents a group chosen from hydroxyl and NR′₂₈R′₂₉ with R′₂₈ and R′₂₉, which may be identical or different, representing the same atoms or groups as R₂₈ and R₂₉ as defined previously;

it being understood that formulae (V) and (V′) comprise at least one sulfonate radical (O)₂S(O⁻)—, M⁺ or one carboxylate radical —C(O)O⁻, M⁺; preferentially sodium sulfonate;

As examples of dyes of formula (V), mention may be made of: Acid Blue 25, Acid Blue 43, Acid Blue 62, Acid Blue 78, Acid Blue 129, Acid Blue 138, Acid Blue 140, Acid Blue 251, Acid Green 25, Acid Green 41, Acid Violet 42, Acid Violet 43, Mordant Red 3; EXT violet No. 2; and as examples of dyes of formula (V′), mention may be made of: Acid Black 48;

d) the nitro dyes of formulae (VI), (VI′) and (VI″):

in which formulae (VI) and (VI′):

R₃₀, R₃₁ and R₃₂, which may be identical or different, represent a hydrogen or halogen atom, or a group chosen from:

-   -   (C₁-C₆)alkyl;     -   (C₁-C₆)alkoxy optionally substituted with one or more hydroxyl         groups, (C₁-C₆)alkylthio optionally substituted with one or more         hydroxyl groups;     -   hydroxyl, mercapto;     -   nitro, nitroso;     -   polyhalo(C₁-C₆)alkyl;     -   R^(o)—C(X)—X′—, R^(o)—X′—C(X)—, R^(o)—X′—C(X)—X″— with R^(o), X,         X′ and X″ as defined previously;     -   (O)₂S(O⁻)—, M⁺ with M⁺ as defined previously;     -   (O)CO⁻—, M⁺ with M⁺ as defined previously;     -   (di)(C₁-C₆)(alkyl)amino;     -   (di)(hydroxy(C₁-C₆)alkyl)amino;     -   heterocycloalkyl such as piperidino, piperazino or morpholino;     -   in particular, R₃₀, R₃₁ and R₃₂ represent a hydrogen atom;     -   R_(c) and R_(d), which may be identical or different, represent         a hydrogen atom or a (C₁-C₆)alkyl group;

W is as defined previously; W particularly represents an —N(H)— group;

ALK represents a linear or branched divalent C₁-C₆ alkylene group; in particular, ALK represents a —CH₂—CH₂— group;

n is 1 or 2;

p represents an integer between 1 and 5 inclusive;

q represents an integer between 1 and 4 inclusive;

u is 0 or 1;

when n is 1, J represents a nitro or nitroso group; particularly nitro;

when n is 2, J represents an oxygen or sulfur atom, or a divalent radical —S(O)_(m)— with m representing an integer 1 or 2; preferentially, J represents an —SO₂— radical;

M′ represents a hydrogen atom or a cationic counterion;

which may be present or absent, represents a benzo group optionally substituted with one or more groups R₃₀ as defined previously; it being understood that formulae (VI) and (VI′) comprise at least one sulfonate radical (O)₂S(O⁻)—, M⁺ or one carboxylate radical —C(O)O⁻, M⁺; preferentially sodium sulfonate;

As examples of dyes of formula (VI), mention may be made of: Acid Brown 13 and Acid Orange 3; as examples of dyes of formula (VI′), mention may be made of: Acid Yellow 1, the sodium salt of 2,4-dinitro-1-naphthol-7-sulfonic acid, 2-piperidino-5-nitrobenzenesulfonic acid, 2-(4′-N,N-(2″-hydroxyethyl)amino-2′-nitro)anilineethanesulfonic acid, 4-p-hydroxyethylamino-3-nitrobenzenesulfonic acid; EXT D&C Yellow 7;

d) the triarylmethane dyes of formula (VII): in which formula (VII):

R₃₃, R₃₄, R₃₅ and R₃₆, which may be identical or different, represent a hydrogen atom or a group chosen from (C₁-C₆)alkyl, optionally substituted aryl and optionally substituted aryl(C₁-C₆)alkyl; particularly a (C₁-C₆)alkyl group and benzyl optionally substituted with an (O)_(m)S(O⁻)—, M⁺ group with M⁺ and m as defined previously;

R₃₇, R₃₈, R₃₉, R₄₀, R₄₁, R₄₂, R₄₃ and R₄₄, which may be identical or different, represent a hydrogen atom or a group chosen from:

-   -   (C₁-C₆)alkyl;     -   (C₁-C₆)alkoxy, (C₁-C₆)alkylthio;     -   (di)(C₁-C₆)(alkyl)amino;     -   hydroxyl, mercapto;     -   nitro, nitroso;     -   R^(o)—C(X)—X′—, R^(o)—X′—C(X)—, R^(o)—X′—C(X)—X″— with R^(o)         representing a hydrogen atom or an alkyl or aryl group; X, X′         and X″, which may be identical or different, representing an         oxygen or sulfur atom, or NR with R representing a hydrogen atom         or a (C₁-C₆)alkyl group;     -   (O)₂S(O⁻)—, M⁺ with M⁺ representing a hydrogen atom or a         cationic counterion;     -   (O)CO⁻—, M⁺ with M⁺ as defined previously;     -   or alternatively two contiguous groups R₄₁ with R₄₂ or R₄₂ with         R₄₃ or R₄₃ with R₄₄ together form a fused benzo group optionally         substituted with one or more groups chosen from i) nitro; ii)         nitroso; iii) (O)₂S(O⁻)—, M⁺; iv) hydroxyl; v) mercapto; vi)         (di)(C₁-C₆)(alkyl)amino; vii) R^(o)—C(X)—X′—; viii)         R^(o)—X′—C(X)—; ix) R^(o)—X′—C(X)—X″—; with M⁺, R^(o), X, X′ and         X″ as defined previously; particularly, R₃₇ to R₄₀ represent a         hydrogen atom, and R₄₁ to R₄₄, which may be identical or         different, represent a hydroxyl group or (O)₂S(O⁻)—, M⁺; and         when R₄₃ with R₄₄ together form a benzo group, it is         preferentially substituted with an (O)₂S(O⁻)— group;     -   it being understood that at least one of the rings G, H, I or I′         comprises at least one sulfonate radical (O)₂S(O⁻)— or a         carboxylate radical —C(O)O⁻; preferentially sulfonate;

As examples of dyes of formula (VII), mention may be made of: Acid Blue 1; Acid Blue 3; Acid Blue 7, Acid Blue 9; Acid Violet 49; Acid Green 3; Acid Green 5 and Acid Green 50;

e) the xanthene-based dyes of formula (VIII):

in which formula (VIII):

R₄₅, R₄₆, R₄₇ and R₄₈, which may be identical or different, represent a hydrogen or halogen atom;

R₄₉, R₅₀, R₅₁ and R₅₂, which may be identical or different, represent a hydrogen or halogen atom, or a group chosen from:

-   -   (C₁-C₆)alkyl;     -   (C₁-C₆)alkoxy, (C₁-C₆)alkylthio;     -   hydroxyl, mercapto;     -   nitro, nitroso;     -   (O)₂S(O⁻)—, M⁺ with M⁺ representing a hydrogen atom or a         cationic counterion;     -   (O)CO⁻—, M⁺ with M⁺ as defined previously;         particularly, R₅₃, R₅₄, R₅₅ and R₄₈ represent a hydrogen or         halogen atom;

G represents an oxygen or sulfur atom or a group NR_(e) with R_(e) as defined previously; particularly, G represents an oxygen atom;

L represents an alkoxide O⁻, M⁺; a thioalkoxide S⁻, M⁺ or a group NR_(f), with R_(f) representing a hydrogen atom or a (C₁-C₆)alkyl group, and M⁺ as defined previously; M⁺ is particularly sodium or potassium;

L′ represents an oxygen or sulfur atom or an ammonium group: N⁺R_(f)R_(g), with R_(f) and R_(g), which may be identical or different, representing a hydrogen atom, a (C₁-C₆)alkyl group or an optionally substituted aryl group; L′ represents particularly an oxygen atom or a phenylamino group optionally substituted with one or more alkyl or (O)_(m)S(O⁻)—, M⁺ groups with m and M⁺ as defined previously;

Q and Q′, which may be identical or different, represent an oxygen or sulfur atom; particularly Q and Q′ represent an oxygen atom;

M⁺ is as defined previously;

As an example of dyes of formula (VIII), mention may be made of: Acid Yellow 73; Acid Red 51; Acid Red 52; Acid Red 87; Acid Red 92; Acid Red 95; Acid Violet 9;

f) the indole-based dyes of formula (IX):

in which formula (IX):

R₅₃, R₅₄, R₅₅, R₅₆, R₅₇, R₅₈, R₅₉ and R₆₀, which may be identical or different, represent a hydrogen atom or a group chosen from:

-   -   (C₁-C₆)alkyl;     -   (C₁-C₆)alkoxy, (C₁-C₆)alkylthio;     -   hydroxyl, mercapto;     -   nitro, nitroso;     -   R^(o)—C(X)—X′—, R^(o)—X′—C(X)—, R^(o)—X′—C(X)—X″— with R^(o)         representing a hydrogen atom or an alkyl or aryl group; X, X′         and X″, which may be identical or different, representing an         oxygen or sulfur atom, or NR with R representing a hydrogen atom         or a (C₁-C₆)alkyl group;     -   (O)₂S(O⁻)—, M⁺ with M⁺ representing a hydrogen atom or a         cationic counterion;     -   (O)CO⁻—, M⁺ with M⁺ as defined previously;

G represents an oxygen or sulfur atom or a group NR_(e) with R_(e) as defined previously; particularly, G represents an oxygen atom;

R_(i) and R_(h), which may be identical or different, represent a hydrogen atom or a (C₁-C₆)alkyl group;

it being understood that formula (IX) comprises at least one sulfonate radical (O)₂S(O⁻)—, M⁺ or one carboxylate radical —C(O)O⁻, M⁺; preferentially sodium sulfonate

As examples of dyes of formula (IX), mention may be made of: Acid Blue 74.

g) the quinoline-based dyes of formula (X):

in which formula (X):

R₆₁ represents a hydrogen or halogen atom or a (C₁-C₆)alkyl group;

R₆₂, R₆₃ and R₆₄, which may be identical or different, represent a hydrogen atom or a group (O)₂S(O⁻)—, M⁺ with M⁺ representing a hydrogen atom or a cationic counterion;

or alternatively R₆₁ with R₆₂, or R₆₁ with R₆₄, together form a benzo group optionally substituted with one or more groups (O)₂S(O⁻)—, M⁺ with M⁺ representing a hydrogen atom or a cationic counterion; it being understood that formula (X) comprises at least one sulfonate radical (O)₂S(O⁻)—, M⁺ preferentially sodium sulfonate.

As examples of dyes of formula (X), mention may be made of: Acid Yellow 2, Acid Yellow 3 and Acid Yellow 5.

More particularly, the dyes of formulae (III) to (VIII) that are useful in the invention are chosen from:

TABLE 1 (C.I. 45380) Acid Red 87 (VIII) (C.I. 10316) Sodium salt of 2,4-dinitro-1-naphthol-7-sulfonic acid (VI′) (C.I. 10383) Acid Orange 3 (VI) (C.I. 13015) Acid Yellow 9/Food Yellow 2 (III) (C.I. 14780) /Direct Red 45/Food Red 13 (III) (C.I. 13711) Acid Black 52 (III) (C.I. 13065) Acid Yellow 36 (III) (C.I. 14700) Sodium salt of 1-hydroxy-2-(2′,4′-xylyl-5-sulfonatoazo)naphthalene-4-sulfonic acid/Food Red 1 (III) (C.I. 14720) Acid Red 14/Food Red 3/Mordant Blue 79 (III) (C.I. 14805) Sodium salt of 4-hydroxy-3-[(2-methoxy-5-nitrophenyl)diaza]-6- (phenylamino)naphthalene-2-sulfonic acid/Acid Brown 4 (III) (C.I. 15510) Acid Orange 7/Pigment Orange 17/Solvent Orange 49 (III) (C.I. 15985) Food Yellow 3/Pigment Yellow 104 (III) (C.I. 16185) Acid Red 27/Food Red 9 (III) (C.I. 16230) Acid Orange 10/Food Orange 4(III) (C.I. 16250) Acid Red 44 (III) (C.I. 17200) Acid Red 33/Food Red 12 (III) (C.I. 15685) Acid Red 184 (III) (C.I. 19125) Acid Violet 3 (III) (C.I. 18055) Sodium salt of 1-hydroxy-2-(4′-acetamidophenylazo)-8-acetamidonaphthalene- 3,6-disulfonic acid/Acid Violet 7/Food Red 11 (III) (C.I. 18130) Acid Red 135 (III) (C.I. 19130) Acid Yellow 27 (IV) (C.I. 19140) Acid Yellow 23/Food Yellow 4 (IV) (C.I. 20170) 4′-(Sulfonato-2″,4″-dimethyl)bis(2,6-phenylazo)-1,3-dihydroxybenzene/Acid Orange 24 (III) (C.I. 20470) Sodium salt of 1-amino-2-(4′-nitrophenylazo)-7-phenylazo-8- hydroxynaphthalene-3,6-disulfonic acid/Acid Black 1 (III) (C.I. 23266) (4-((4-methylphenyl)sulfonyloxy)phenylazo)-2,2′-dimethyl-4-((2-hydroxy-5,8- disulfonato)naphthylazo)biphenyl/Acid Red 111 (III′) (C.I. 27755) Food Black 2 (III) (C.I. 25440) 1-(4′-Sulfonatophenylazo)-4-((2″-hydroxy-3″-acetylamino-6″,8″- disulfonato)naphthylazo)-6-sulfonatonaphthalene (tetrasodium salt)/Food Black 1 (III) (C.I. 42090) Acid Blue 9 (VII) (C.I. 60730) Acid Violet 43 (V) (C.I. 61570) Acid Green 25 (V) (C.I. 62045) Sodium salt of 1-amino-4-cyclohexylamino-9,10-anthraquinone-2-sulfonic acid/ Acid Blue 62 (V) (C.I. 62105) Acid Blue 78 (V) (C.I. 14710) Sodium salt of 4-hydroxy-3-((2-methoxyphenyl)azo)-1-naphthalenesulfonic acid/ Acid Red 4 (III) 2-Piperidino-5-nitrobenzenesulfonic acid (VI′) 2-(4′-N,N-(2″-Hydroxyethyl)amino-2′-nitro)anilineethanesulfonic acid (VI′) 4-β-Hydroxyethylamino-3-nitrobenzenesulfonic acid (VI′) (C.I. 42640) Acid Violet 49 (VII) (C.I. 42080) Acid Blue 7 (VII) (C.I. 58005) Sodium salt of 1,2-dihydroxy-3-sulfoanthraquinone/Mordant Red 3 (V) (C.I. 62055) Sodium salt of 1-amino-9,10-dihydro-9,10-dioxo-4-(phenylamino) 2- anthracenesulfonic acid/Acid Blue 25 (V) (C.I. 14710) Sodium salt of 4-hydroxy-3-((2-methoxyphenyl)azo)-1-naphthalenesulfonic acid/ Acid Red 4 (III)

Most of these dyes are described in particular in the Color Index published by The Society of Dyers and Colorists, P.O. Box 244, Perkin House, 82 Grattan Road, Bradford, Yorkshire, BD1 2LU England.

The anionic dyes that are most particularly preferred are the dyes designated in the Color Index under the code C.I. 58005 (monosodium salt of 1,2-dihydroxy-9,10-anthraquinone-3-sulfonic acid), C.I. 60730 (monosodium salt of 2-[(9,10-dihydro-4-hydroxy-9,10-dioxo-1-anthracenyl)amino]-5-methylbenzenesulfonic acid), C.I. 15510 (monosodium salt of 4-[(2-hydroxy-1-naphthalenyl)azo]benzenesulfonic acid), C.I. 15985 (disodium salt of 6-hydroxy-5-[(4-sulfophenyl)azo]-2-naphthalenesulfonic acid), C.I. 17200 (disodium salt of 5-amino-4-hydroxy-3-(phenylazo)-2,7-naphthalenedisulfonic acid), C.I. 20470 (disodium salt of 1-amino-2-(4′-nitrophenylazo)-7-phenylazo-8-hydroxy-3,6-naphthalenedisulfonic acid), C.I. 42090 (disodium salt of N-ethyl-N-[4-[[4-[ethyl(3-sulfophenyl)methyl]amino]phenyl](2-sulfophenyl)methylene]-2,5-cyclohexadien-1-ylidene]-3-sulfobenzenemethanaminium hydroxide, inner salt), C.I. 61570 (disodium salt of 2,2′-[(9,10-dihydro-9,10-dioxo-1,4-anthracenediyl)diimino]bis[5-methyl]benzenesulfonic acid).

Use may also be made of compounds corresponding to the mesomeric or tautomeric forms of structures (III) to (X).

Preferably, the anionic direct dye(s) of the invention are chosen from the dyes of formula (V) such as Acid Violet 43.

The anionic direct dye(s) particularly represent from 0.001% to 20% by weight approximately relative to the total weight of the composition, and preferentially from 0.005% to 10% by weight approximately. More particularly, the anionic dye(s) represent from 0.01% to 5% by weight.

Among the natural direct dyes that may be used according to the invention, mention may be made of lawsone, juglone, alizarin, purpurin, carminic acid, kermesic acid, purpurogallin, protocatechaldehyde, indigo, isatin, curcumin, spinulosin, apigenidin, orceins, brazilin, brazilein, hematin and hematoxylin. Extracts or decoctions containing these natural dyes and notably henna-based poultices or extracts may also be used.

Preferably, the direct dye(s) a) have a solubility in water at a temperature of 22° C. and at atmospheric pressure (760 mmHg, i.e. 1.013×10⁵ Pa) of less than 5% by weight, more preferentially less than 1% by weight and even more preferentially less than 0.5% by weight.

The direct dye(s) a) advantageously represent from 0.001% to 10% by weight, preferentially from 0.05% to 5% by weight relative to the total weight of the composition comprising them, more preferentially from 0.3% to 3% by weight relative to the total weight of the composition comprising them.

a) Unsaturated Heterocyclic Salts of Formula (A):

The second ingredient b) used in the process and the composition of the invention is an unsaturated heterocyclic salt of formula (A) as defined previously.

According to a particular embodiment of the invention, the salt(s) of formula (A) are chosen from those of formulae (I) and (II) below, and also the tautomeric forms thereof:

in which formulae (I) and (II):

R₁ represents a linear or branched, saturated or unsaturated (C₁-C₁₂) hydrocarbon-based group optionally substituted with one or more groups chosen from hydroxyl, amino, (C₁-C₆)dialkylamino, (C₁-C₆)alkylamino, carboxyl, carboxylate, carbamide, (C₁-C₄)alkoxy, —SO₃H, sulfonate and phenyl;

R′₁ represents a hydrogen atom, a linear or branched, saturated or unsaturated (C₁-C₁₂) hydrocarbon-based group optionally substituted with one or more groups chosen from hydroxyl, amino, (C₁-C₆)dialkylamino, (C₁-C₆)alkylamino, carboxyl, carboxylate, carbamide, (C₁-C₄)alkoxy, —SO₃H, sulfonate and phenyl; and

R₂ represents a hydroxyl group, a linear or branched, saturated or unsaturated (C₁-C₁₂) hydrocarbon-based group optionally substituted with one or more groups chosen from hydroxyl, (C₁-C₄)alkoxy, —SO₃H, sulfonate and benzene;

n is 0, 1, 2 or 3; preferably, n is 0 or 1;

Y′ represents an anionic counterion;

it being understood that:

-   -   when one of the hydrocarbon-based groups of R₁, R′₁ or R₂ is         substituted with a carboxylate or sulfonate group, then Y⁻ is         absent to ensure the electrical neutrality of the salt of         formula (A), and     -   when n is equal to 2 or 3, then the substituents are identical         or different.

According to a particular embodiment of the invention, the salts of formulae (A), (I) and (II) are such that R₁ represents a linear or branched, preferably linear, saturated or unsaturated (C₁-C₁₀) hydrocarbon-based group, optionally substituted with one or more groups chosen from hydroxyl, (C¹C₄)alkoxy, —SO₃H, —SO₃ ⁻ and phenyl; preferentially, R₁ represents a linear or branched (C₁-C₈)alkyl group. More preferentially, R₁ represents a linear (C₁-C₈)alkyl group, optionally substituted with one or more hydroxyl, phenyl, —SO₃H and —SO₃ ⁻ groups, or alternatively R₁ represents a linear or branched (C₂-C₆)alkenyl group, preferably vinyl or allyl.

According to a particular embodiment, the salt(s) of formula (I) are such that R′₁ represents a hydrogen atom or a linear or branched, saturated or unsaturated (C₁-C₈) hydrocarbon-based group optionally substituted with one or more groups chosen from hydroxyl, (C₁-C₂)alkoxy, —SO₃H, —SO₃ ⁻ and phenyl. Preferentially, R′₁ represents a hydrogen atom or a linear or branched, more preferentially linear, saturated (C₁-C₆) hydrocarbon-based group, particularly methyl.

According to a particular embodiment, the salt(s) of formula (I) are such that R₂ represents a linear or branched, saturated (C₁-C₆) hydrocarbon-based group such as methyl; preferably, n is 1 and R₂ is in position 2.

According to a particular embodiment, the salt(s) of formula (II) are such that R₁ represents a linear or branched, saturated or unsaturated (C₁-C₁₂) hydrocarbon-based group; in particular, R₁ represents a linear or branched (C₁-C₈)alkyl group, preferably, R₁ represents a (C₁-C₄)alkyl group such as methyl.

According to a particular embodiment, the salts of formula (II) are such that R₂ represents a hydroxyl group, a linear or branched, saturated or unsaturated (C₁-C₁₂) hydrocarbon-based group, optionally substituted with one or more hydroxyl, (C₁-C₄)alkoxy, —SO₃H, —SO₃ ⁻ and phenyl groups; preferentially, R₂ represents a hydroxyl group or a (C₁-C₄)alkyl group such as methyl; R₂ is preferably positioned in position 2′, 3′ or 4′.

According to a particular embodiment, the salt(s) of formula (A), (I) or (II) in which Y⁻ represents an anionic counterion chosen from i) halides such as chloride, bromide, ii) hydrogen sulfates, iii) (bis)(poly)halo(C₁-C₁₂)(alkyl)sulfonylimides such as bis(trifluoromethylsulfonyl)imide and bis(fluorosulfonyl)imide, iv) (C₁-C₁₂)alkyl sulfates, v) (poly)halophosphates such as hexafluorophosphate, vi) (C₁-C₁₂)(alkyl)phosphates, phosphate, vii) (poly)haloborates such as tetrafluoroborate, viii) carbonate, ix) bicarbonate, x) (C₁-C₁₂)alkylcarbonates, xi) dicyanamide, xii) nitrate, xiii) thiocyanate, xiv) formate, xv) (C₁-C₁₂)alkylcarboxylates in which the (C₁-C₁₂)alkyl group may be substituted with one or more halogen atoms or groups chosen from hydroxyl, (C₁-C₆)(di)(alkyl)amino, phenyl, imidazole, (C₁-C₄)alkylcarbonyl, (C₁-C₄)alkylcarbonyloxy, (C₁-C₄)alkylcarbonylamino, guanidine, thiol, —SO₃H, (C₁-C₈)alkoxy such as trifluoroacetate; xvi) (C₆-C₁₂)arylcarboxylates in which the aryl group may be substituted with one or more halogen atoms or groups chosen from hydroxyl, (C₁-C₆)(di)(alkyl)amino, phenyl, imidazole, (C₁-C₄)alkylcarbonyl, (C₁-C₄)alkylcarbonyloxy, (C₁-C₄)alkylcarbonylamino, guanidine, thiol, —SO₃H, (C₁-C₈)alkoxy; xvii) (C₁-C₁₂)alkylsulfonates in which the (C₁-C₁₂)alkyl group may be substituted with one or more halogen atoms or groups chosen from hydroxyl, (C₁-C₆)(di)(alkyl)amino, phenyl, imidazole, (C₁-C₄)alkylcarbonyl, (C₁-C₄)alkylcarbonyloxy, (C₁-C₄)alkylcarbonylamino, guanidine, thiol, —SO₃H, (C₁-C₈)alkoxy such as triflate, in particular (C₁-C₆)alkylsulfonates such as methylsulfonate or mesylate; and xviii) (C₆-C₁₂)arylsulfonates in which the aryl group may be substituted with one or more halogen atoms or groups chosen from hydroxyl, (C₁-C₆)(di)(alkyl)amino, phenyl, imidazole, (C₁-C₄)alkylcarbonyl, (C₁-C₄)alkylcarbonyloxy, (C₁-C₄)alkylcarbonylamino, guanidine, thiol, —SO₃H, (C₁-C₈)alkoxy such as benzenesulfonate and toluenesulfonate ortosylate.

Preferentially, Y⁻ represents:

more preferentially, Y⁻ is chosen from i), xvii) and xviii); more preferentially, Y⁻ is chosen from chloride, bromide, methyl sulfate and tosylate.

According to a preferred embodiment of the invention, the salt(s) of formula (A), (I) or (II) are chosen from compounds 1 to 40:

with Y′ representing an anionic counterion as defined previously; preferably, the salts of formula (A), (I) or (II) are chosen from compounds 2, 3, 4, 5, 34 and 36, more preferentially 2, 4, 5 and 36.

According to a particular embodiment of the invention, the heterocyclic salt(s) of the invention are ionic liquids.

For the purposes of the present invention, the term “ionic liquid” means a salt of an organic compound, said salt having a melting point of less than or equal to 150° C., preferably less than 100° C. Preferably, the salt remains liquid up to 300° C., and more preferentially the salt is liquid at room temperature, i.e. at a temperature of less than or equal to 50° C. and greater than 0° C.

The melting point is measured by differential calorimetric analysis, with a temperature increase rate of 10° C./minute, the melting point then being at a temperature corresponding to the top of the endothermic melting peak obtained during the measurement.

The heterocyclic salt(s) (A) of the invention are preferably present in proportions ranging from 1% to 99.5% by weight, preferentially from 3% to 90%, even more preferentially from 10% to 90% by weight, better still from 20% to 80% by weight, more preferentially from 30% to 70% and even more preferentially from 40% to 60% relative to the total weight of the composition comprising them.

The Process for Dyeing Keratin Materials

The process for dyeing keratin materials, in particular keratin fibers, notably human keratin fibers such as the hair, according to the invention uses ingredients a) and b) which are applied to said fibers, together or separately, i.e. sequentially.

According to one embodiment of the invention, ingredients a) and b) are applied together to said materials. According to one variant, ingredients a) and b) are in a cosmetic composition which is applied to the keratin materials. Said cosmetic composition comprises one or more direct dyes a) as defined previously and one or more unsaturated heterocyclic salts of formula (A) as defined previously. Preferably, the cosmetic composition comprising a) and b) is aqueous. More preferentially, the composition comprises only the ingredients a), b) and water.

According to another embodiment, the process for dyeing keratin fibers of the invention comprises i) a first step of applying to the keratin materials a composition comprising a) one or more direct dyes as defined previously and then ii) a step of applying to the keratin materials a composition comprising b) one or more unsaturated heterocyclic salts of formula (A) as defined previously. Preferably, the composition comprising a) and the composition comprising b) are aqueous.

According to another particular embodiment, the process for dyeing keratin materials of the invention comprises i) a first step of applying a composition comprising b) one or more unsaturated heterocyclic salts of formula (A) as defined previously and then ii) a step of applying to the keratin materials a composition comprising a) one or more direct dyes as defined previously. Preferably, the composition comprising a) and the composition comprising b) are aqueous.

The composition(s) may be applied to wet or dry keratin materials and in particular wet or dry keratin fibers.

Preferably, the application to the keratin materials of the composition(s) comprising a) and b) as defined previously is preferably performed at room temperature, i.e. at a temperature between 25° C. and 30° C.

According to an advantageous variant of the invention, after application of ingredients a) and b), the keratin materials are rinsed, optionally shampooed and then dried or left to dry, for example at a temperature of greater than or equal to 30° C.

According to a particular embodiment, this temperature is greater than 40° C. According to a particular embodiment, this temperature is greater than 45° C. and less than 220° C.

Preferably, if the keratin materials are dried, they are dried, in addition to a supply of heat, with a flow of air.

During drying, a mechanical action may be exerted on the locks, such as combing, brushing or running the fingers through. This operation may similarly be performed once the keratin materials have been dried, naturally or otherwise.

The keratin fiber drying step of the process of the invention may be performed with a drying device such as a hood, a hairdryer, a straightening iron or a Climazon.

When the drying step is performed on keratin fibers, it may then be performed with a hood or a hairdryer; the drying temperature is between 40 and 110° C. and preferably between 50 and 90° C.

When the drying step is performed on keratin fibers, it may then be performed with a straightening iron; the drying temperature is between 110 and 220° C. and preferably between 140 and 200° C. Once the drying is complete, final rinsing or shampooing may optionally be performed.

The composition(s) applied to the wet or dry keratin materials, preferably with a weight ratio of the amount of composition applied relative to the amount of hair of between 0.1 and 10, more particularly between 0.2 and 5.

The Compositions

Another subject of the invention is a cosmetic composition which comprises a) one or more direct dyes as defined previously and b) one or more unsaturated heterocyclic salts of formula (A) as defined previously. The composition is preferably aqueous.

The composition(s) of the invention are cosmetic, i.e. they are in a cosmetic medium.

The Cosmetic Medium:

The term “cosmetic medium” means a medium that is suitable for dyeing keratin fibers, also known as a dye support, which is a cosmetic medium generally formed from water or a mixture of water and one or more organic solvents or a mixture of organic solvents. Preferably, the composition comprises water and in a content notably of between 5% and 95% inclusive relative to the total weight of the composition. More preferentially, the composition(s) of the invention do not comprise any ingredients other than a) and b).

The term “organic solvent” means an organic substance capable of dissolving another substance without chemically modifying it.

Organic Solvents:

Examples of organic solvents that may be mentioned include lower C₁-C₄ alkanols, such as ethanol and isopropanol; polyols and polyol ethers, for instance 2-butoxyethanol, propylene glycol, propylene glycol monomethyl ether and diethylene glycol monoethyl ether and monomethyl ether, and also aromatic alcohols, for instance benzyl alcohol or phenoxyethanol, and mixtures thereof.

The organic solvents are preferably present in proportions preferably between inclusively 0.1% and 40% by weight approximately relative to the total weight of the dye composition, more preferentially between 1% and 30% by weight approximately and even more particularly between inclusively 5% and 25% by weight relative to the total weight of the composition.

The composition(s) of the invention may also comprise one or more compounds that are liquid at room temperature and at atmospheric pressure other than the cationic heterocyclic salts (A) of the invention. The liquid compound is preferably a solvent and in particular a solvent chosen from water, aliphatic C₁-C₄ alcohols such as ethanol and isopropanol, organic solvents which are soluble or dispersible in water such as acetone, propylene carbonate, benzyl alcohol, glycol ether derivatives, polyols such as glycerol, propylene glycol and polyethylene glycols. More preferentially, said liquid compound is a polar solvent, even more preferentially a polar protic solvent.

The pH

The pH of the composition(s) comprising ingredients a) and b) is generally between 3 and 13, preferably between 5 and 10 and more preferentially between 6 and 9.5. The pH of this or these compositions may be adjusted with acidifying or basifying agents conventionally used in cosmetics.

Among the acidifying agents, examples that may be mentioned include the organic acids already mentioned previously, or mineral acids.

The term “mineral acid” means any acid derived from a mineral compound. Among the mineral acids, mention may be made of hydrochloric acid, orthophosphoric acid, sulfuric acid, sulfonic acids and nitric acid.

Use may notably be made of mineral or organic acids such as hydrochloric acid, orthophosphoric acid, sulfuric acid, carboxylic acids, for instance acetic acid, tartaric acid, citric acid or lactic acid, and sulfonic acids.

Among the basifying agents, examples that may be mentioned include aqueous ammonia, alkali metal carbonates, alkanolamines, such as monoethanolamine, diethanolamine and triethanolamine and derivatives thereof, sodium hydroxide, potassium hydroxide and the compounds of formula (B) below:

in which formula (B) W is a (C₁-C₆)alkylene group optionally substituted with one or more hydroxyl groups, R_(a), R_(b), R_(c) and R_(d), which may be identical or different, represent a hydrogen atom or a C₁-C₄ alkyl group optionally substituted with one or more hydroxyl groups. Preferably, the pH modifiers may be chosen from alkaline agents, such as aqueous ammonia, monoethanolamine, diethanolamine, triethanolamine, 1,3-propanediamine or an alkaline hydroxide, such as 2-amino-2-methyl-1-propanol, or else acidifying agents, such as phosphoric acid or hydrochloric acid.

The composition(s) comprising ingredients a) and b) may be in liquid form, in the form of a serum, in thickened form, in particular a gel, a cream, a wax or a paste, or in foam form.

The composition(s) of the invention may also comprise one or more active agents other than ingredients a) and b).

The composition used in step a) may also contain one or more additional cosmetic active agents other than solvents, reducing agents, acidic or alkaline agents and salts.

These active agents are generally chosen from nonionic, anionic, cationic or amphoteric surfactants, cationic, anionic, nonionic or zwitterionic, associative or nonassociative thickening polymers of natural or synthetic origin, silicones in the form of oils, gums or resins or non-silicone plant, mineral or synthetic oils, UV-screening agents, fillers, such as nacres and metal oxides such as titanium dioxides, clays, fragrances, peptizers, vitamins and preserving agents.

A subject of the invention is also a multi-compartment device or kit, comprising at least a first compartment which contains a) at least one direct dye as defined previously, and at least a second compartment which contains b) at least one heterocyclic salt of formula (A) as defined previously.

The invention is illustrated by the example which follows without, however, being limiting in nature.

EXAMPLES Dyes Evaluated:

Heterocyclic Salts:

Preparation of the Compositions:

The comparative compositions (Comp. 1 to 6) and the compositions of the invention (Inv. 1 to 6) were prepared by adhering to the amounts described in the tables below:

TABLE 3 Ingredients Comp 1 Inv 1 Comp. 2 Inv. 2.1 Inv. 2.2 Comp. 3 Inv. 3 Dye 1 (g %)  0.5 0.5 — — — — — Dye 2 (g %) — — 0.5 0.5 0.5 — — Dye 3 (g %) — — — — — 0.5 0.5 Ethylmethylimidazolium — 5 5 — chloride (g %) Ethylmethylimidazolium — — — — 5 — — tosylate (g %) Butylpyridinium — — — — — — 50 chloride (g %) Water qs 100 qs 100 qs 100 qs 100 qs 100 qs 100 qs 100

TABLE 4 Ingredients Comp 4 Inv 4.1 Inv 4.2 Comp 5 Inv 5.1 Inv 5.2 Inv 5.3 Dye 4 (g %) 0.5  0.5  0.5 — — — — Dye 5 (g %) — — — 0.5  0.5  0.5  0.5 Ethylmethylimidazolium — 50 — — 50 — — tosylate (g %) Ethylmethylimidazolium — — 50 — — — — bromide (g %) Ethylmethylimidazolium — — — — — 50 — methyl sulfate (g %) Butylmethylimidazolium — — — — — — 50 methyl sulfate (g %) Water qs 100 qs 100 qs 100 qs 100 qs 100 qs 100 qs 100

TABLE 5 Ingredients Comp 6 Inv 6.1 Inv 6.2 Inv 6.3 Inv 6.4 Dye 6 (g %) 0.5  0.5  0.5  0.5  0.5 Hexylmethylimidazolium — 10 — — — chloride (g %) 2-Hydroxyethylmethyl- — — 10 — — imidazolium chloride (g %) Butylmethylimidazolium — — — 10 — bromide (g %) 3-Hydroxy-N- — — — — 10 ethylpyridinium bromide (g %) Water qs 100 qs 100 qs 100 qs 100 qs 100

TABLE 6 Ingredients Comp 7 Inv 7.1 Inv 7.2 Inv 7.3 Inv 7.4 Inv 7.5 Dye 7 (g %) 0.5  0.5  0.5  0.5  0.5  0.5 Hexylmethylimidazolium chloride — 10 — — — — (g %) 2-Hydroxyethylmethylimidazolium — — 10 — — — chloride (g %) Butylmethylimidazolium bromide — — — 10 — — (g %) Butylmethylimidazolium acetate — — — — 10 — (g %) 3-Hydroxy-N-ethylpyridinium — — — — — 10 bromide (g %) Water qs 100 qs 100 qs 100 qs 100 qs 100 qs 100

TABLE 7 Ingredients Comp 8 Inv 8.1 Inv 8.2 Inv 8.3 Dye 6 (g %) 0.5 0.5 0.5 0.5 2-Hydroxyethylmethylimidazolium — 10 — — chloride (g %) Butylmethylimidazolium — — 10 — bromide (g %) Butylmethylimidazolium — — — 10 acetate (g %) Water qs 100 qs 100 qs 100 qs 100

Application on Locks: Protocol 1:

5 g of Comparative composition (Comp, x) or of composition according to the invention (Inv. x) are applied to 0.5 g of natural hair containing 90% white hairs, at 33° C. for 30 minutes. The hair is then rinsed, shampooed and dried.

Protocol 2:

1 g of Comparative composition (Comp, x) or of composition according to the invention (Inv. x) is applied to 0.5 g of natural hair containing 90% white hairs, at 27° C. for 30 minutes. The hair is then rinsed, shampooed and dried.

Protocol 3:

The pH of the Comparative composition (Comp, x) or of the composition according to the invention (Inv. x) is adjusted to 3 with lactic acid and 1 g of formula is then applied to 0.5 g of natural hair containing 90% white hairs, at 27° C. for 30 minutes. The hair is then rinsed, shampooed and dried.

Protocol 4:

The pH of the Comparative composition (Comp, x) or of the composition according to the invention (Inv. x) is adjusted to 7 with aqueous ammonia and 1 g of formula is then applied to 0.5 g of natural hair containing 90% white hairs, at 27° C. for 30 minutes. The hair is then rinsed, shampooed and dried.

Protocol 5:

1 g of Comparative composition (Comp, x) or of composition according to the invention (Inv. x) is applied to 0.5 g of natural hair containing 90% white hairs, at 27° C. for 30 minutes, at a pH equal to 9.5. The hair is then rinsed, shampooed and dried.

Protocol 6:

1 g of Comparative composition (Comp, x) or of composition according to the invention (Inv. x) is applied to 0.5 g of natural hair containing 90% white hairs, at 33° C. for 30 minutes. The hair is then rinsed, shampooed and dried.

Protocol 7:

1 g of Comparative composition (Comp, x) or of composition according to the invention (Inv. x) is applied to 0.5 g of natural hair containing 90% white hairs, at 33° C. for 30 minutes, at a pH equal to 9.5. The hair is then rinsed, shampooed and dried.

Colorimetric Measurements:

The color build-up (ΔE*) was evaluated in the CIE L* a* b* system using a Minolta Spectrophotometer CM3610A colorimeter, (illuminant D65). In this L*a*b* system, L* represents the intensity of the color, a* indicates the shade of the color on the green/red color axis and b* indicates the shade of the color on the blue/yellow color axis. The lower the value of L*, the darker or more intense the color. The higher the value of a*, the redder the shade, and the higher the value of b*, the bluer the shade.

In the table below, the value of ΔE* is calculated from the values of L*a*b* according to the following equation:

ΔE*=√{square root over ((L*−L ₀*)²+(a*−a ₀*)²+(b*−b ₀*)²)}

In the equation, L*, a* and b* represent the values measured on the locks after treatment by means of each of the protocols 1 to 4 above, and L₀*, a₀* and b₀* represent the values measured on untreated control locks.

The higher the ΔE* value, the better the color build-up or variation.

The results are given in the table below.

Dyeing Results:

The various build-up results obtained are given in the table below:

TABLE 6 Protocol ΔE build-up Comparative 1 1 21.1 Invention 1 1 31.5 Protocol L ΔE build-up Comparative 2 2 59.3 8.4 Invention 2.1 2 53.1 13.7 Invention 2.2 2 53.7 14.0 Comparative 3 3 53.0 15.0 Invention 3 3 52.3 17.6 Comparative 4 4 59.7 4.3 Invention 4.1 4 55.3 14.6 Invention 4.2 4 57.4 12.4 Comparative 5 4 55.62 11.42 Invention 5.1 4 45.2 23.5 Invention 5.2 4 46.8 21.5 Invention 5.3 4 51.1 15.62 Comparative 6 6 59.8 5.6 Invention 6.1 6 57.4 16.2 Invention 6.2 6 62 11 Invention 6.3 6 55.8 11.9 Invention 6.4 6 61.8 11.6 Comparative 7 7 50.2 16.3 Invention 7.1 7 32.4 38 Invention 7.2 7 36.8 32 Invention 7.3 7 33.9 36.5 Invention 7.4 7 42.5 23.9 Invention 7.5 7 39 28.1 Comparative 8 7 57.6 6.1 Invention 8.1 7 59.9 23.7 Invention 8.2 7 57.8 15.3 Invention 8.3 7 59 18.1

It is seen from the above test results that the color build-up is significantly improved by the presence of the saturated heterocyclic salts of formula (A), irrespective of the pH tested. Moreover, the colors obtained are very vivid. 

1. A process for dyeing keratin materials, in particular keratin fibers, preferably human keratin fibers such as the hair, using: a) at least one direct dye; and b) at least one heterocyclic salt of formula (A) and also the optical, geometrical or tautomeric isomers thereof, and the solvates such as hydrates:

in which formula (A): Het represents a 5- to 10-membered (preferentially 5- or 6-membered) cationic unsaturated aromatic heterocyclic group comprising, besides the ammonium, from 1 to 3 heteroatoms, preferentially 1 or 2 nitrogen or oxygen atoms, preferably 1 nitrogen atom, said heterocyclic group being optionally substituted with one or more groups R′₁ or R₂; R₁ and R′₁, which may be identical or different, represent a linear or branched, saturated or unsaturated (C₁-C₁₂) hydrocarbon-based group optionally substituted notably with one or more groups chosen from hydroxyl, amino, (C₁-C₆)dialkylamino, (C₁-C₆)alkylamino, carboxyl, carboxylate, carbamide, (C₁-C₄)alkoxy, —SO₃H, sulfonate and phenyl; R₂ represents a hydroxyl radical, an amino radical, a linear or branched, saturated or unsaturated (C₁-C₁₂) hydrocarbon-based group optionally substituted notably with one or more groups chosen from hydroxyl, amino, (C₁-C₆)dialkylamino, (C₁-C₆)alkylamino, carboxyl, carboxylate, carbamide, (C₁-C₄)alkoxy, —SO₃H, sulfonate and phenyl; and Y⁻ represents an anionic counterion; it being understood that: when one of the hydrocarbon-based groups of R₁, R′₁ or R₂ is substituted with a carboxylate or sulfonate group, then Y⁻ is absent to ensure the electrical neutrality of the salt of formula (A), and ingredients a) and b) are applied to said materials, together or separately, i.e. sequentially; preferably, ingredients a) and b) are applied together to said fibers.
 2. The process as claimed in the preceding claim, in which the direct dyes a) are neutral, cationic or anionic direct dyes chosen from: acridines; acridones; anthranthrones; anthrapyrimidines; anthraquinones; azines; (poly)azos or azos, hydrazono or hydrazones, in particular arylhydrazones; azomethines; benzanthrones; benzimidazoles; benzimidazolones; benzindoles; benzoxazoles; benzopyrans; benzothiazoles; benzoquinones; bis-isoindolines; carboxanilides; coumarins; cyanines, such as (di)azacarbocyanines, (di)azahemicyanines, hemicyanines or tetraazacarbocyanines; (di)azines; bis-azines; (di)oxazines; (di)thiazines; (di)phenylamines; (di)phenylmethanes; (di)ketopyrrolopyrroles; flavonoids, such as flavanthrones and flavones; fluorindines; formazans; indamines; indanthrones; indigoids, thioindigoids and pseudoindigoids; indophenols; indoanilines; isoindolines; isoindolinones; isoviolanthrones; lactones; (poly)methines, such as dimethines of stilbene or styryl types; naphthalimides; naphthanilides; naphtholactams; naphthoquinones; nitro, notably nitro(hetero)aromatics; oxadiazoles; oxazines; perilones; perinones; perylenes; phenazines; phenoxazines; phenothiazines; phthalocyanines; polyenes/carotenoids; porphyrins; pyranthrones; pyrazolanthrones; pyrazolones; pyrimidinoanthrones; pyronines; quinacridones; quinolines; quinophthalones; squaranes; tetrazolines; thiazines; thiopyronines; triarylmethanes or xanthenes and natural direct dyes; more preferentially chosen from anthraquinones, (poly)azos, azomethines and stilbenes.
 3. The process as claimed in claim 1 or 2, in which the direct dye(s) a) are neutral direct dyes; preferably chosen from the hydrazono dyes of formulae (IIIa) and (III′a), the azo and styryl dyes (IVa), the diazo and distyryl dyes (IV′a) and (IV″a), the anthraquinone dyes (Va) and the azomethine dyes (VIa) and (VI′a) below:

in which formulae (IIIa), (III′a), (IVa), (IV′a), (IV″a), (Va), (VIa) and (VI′a): Ar represents an aryl radical, such as phenyl or naphthyl, substituted with at least one electron-donating group such as i) optionally substituted (C₁-C₈)alkyl, ii) optionally substituted (C₁-C₈)alkoxy, iii) (di)(C₁-C₈)(alkyl)amino optionally substituted on the alkyl group(s) with a hydroxyl group, iv) aryl(C₁-C₈)alkylamino, v) optionally substituted N—(C₁-C₈)alkyl-N-aryl(C₁-C₈)alkylamino or, as a variant, Ar represents a julolidine group; Ar′ represents an optionally substituted divalent (hetero)arylene group such as phenylene, particularly para-phenylene, or naphthalene, which is optionally substituted, preferably with one or more (C₁-C₈)alkyl, hydroxyl or (C₁-C₈)alkoxy groups; Ar″ represents a (hetero)aryl radical, which is optionally substituted, preferably with at least i) an electron-withdrawing group such as nitro, nitroso, —C(X)—X′—R′ or ii) a (di)(C₁-C₆)(alkyl)amino group, iii) hydroxyl, iv) (C₁-C₆)alkoxy; (hetero)aryl is particularly chosen from imidazolyl, triazolyl, indolyl or pyridyl or phenyl optionally substituted with at least one group chosen from nitro, nitroso and amino, preferably substituted in the position para to the phenyl group; X, X′ and X″, which may be identical or different, represent an oxygen or sulfur atom, or a group NR″, preferably an oxygen atom; R₁, R², R³ and R⁴, which may be identical or different, represent a hydrogen or halogen atom, or a group chosen from hydroxyl, thiol, (C₁-C₄)alkyl, (C₁-C₄)alkoxy, (di)(C₁-C₄)(alkyl)amino, nitro and nitroso; R′ and R″ represent a (C₁-C₄)alkyl group; R_(a) and R_(b), which may be identical or different, represent a hydrogen atom or a (C₁-C₈)alkyl group, which is optionally substituted, preferably with a hydroxyl group; or, as a variant, the substituent R_(a) with a substituent of Ar″ and/or R_(b) with a substituent of Ar and/or R_(a) with R_(b) form, together with the atoms that bear them, a (hetero)cycloalkyl; particularly, R_(a) and R_(b) represent a hydrogen atom or a (C₁-C₄)alkyl group, which is optionally substituted with a hydroxyl group; T and T′, which may be identical or different, represent a group C(R_(a)) or N, preferably N; and L represents a divalent group -ALK-, —C(X)-ALK-, -ALK—C(X)— or —C(X)-ALK—C(X)— with ALK representing a linear or branched (C₁-C₆)alkylene group, such as methylene, R₂₂, R₂₃, R₂₄, R₂₅, R₂₆ and R₂₇, which may be identical or different, represent a hydrogen or halogen atom, or a group chosen from: (C₁-C₆)alkyl; hydroxyl, mercapto; (C₁-C₆)alkoxy, (C₁-C₆)alkylthio; aryloxy or arylthio; aryl(C₁-C₆)(alkyl)amino; (di)(C₁-C₆)(alkyl)amino; (di)(hydroxy(C₁-C₆)alkyl)amino; Z′ represents a hydrogen atom or a group NR₂₈R₂₉ with R₂₈ and R₂₉, which may be identical or different, representing a hydrogen atom or a group chosen from: (C₁-C₆)alkyl; polyhydroxy(C₁-C₆)alkyl such as hydroxyethyl; aryl optionally substituted with one or more groups, particularly i) (C₁-C₆)alkyl; iii) R^(o)—C(X)—X′—, R^(o)—X′—C(X)—, R^(o)—X′—C(X)—X″— with R^(o) representing a (C₁-C₆)alkyl group, iv) a sulfonate; cycloalkyl; notably cyclohexyl; Z represents a group chosen from hydroxyl and NR′₂₈R′₂₉ with R′₂₈ and R′₂₉, which may be identical or different, representing the same atoms or groups as R₂₈ and R₂₉ as defined previously; in particular, the direct dyes of formula (IV″a) are of formula (IV′″a), and also the optical, geometrical or tautomeric isomers thereof, the organic or mineral acid or base salts thereof, and solvates thereof such as hydrates:

in which formula (IV″′a): R₁ and R₃, which may be identical or different, preferably identical, represent a hydrogen atom, a (C₁-C₄)alkyl group such as methyl or a sugar such as glucosyl, preferably a hydrogen atom; R₂ and R₄, which may be identical or different, preferably identical, represent a hydrogen atom, a (C₁-C₄)alkyl or (C₁-C₄)alkoxy group or an —O-sugar group such as —O-glucosyl, preferably (C₁-C₄)alkoxy; such as methoxy; X, which may be identical or different, preferably identical, represents an oxygen or sulfur atom or N—R with R representing a hydrogen atom, preferably an oxygen atom; ALK represents a (C₁-C₄) alkylene group such as methylene or ethylene, preferably methylene.
 4. The process as claimed in the preceding claim, in which the direct dyes a) are neutral direct dyes chosen from:

and also the organic or mineral acid or base salts thereof, the optical or geometrical isomers thereof, and the solvates thereof such as hydrates.
 5. The process as claimed in any one of the preceding claims, in which the direct dyes a) are chosen from the anionic direct dyes of formulae (III), (III′), (IV), (IV′), (V), (V′), (VI), (VI′), (VII), (VIII), (IX) and (X) below: a) the diaryl anionic azo dyes of formula (III) or (III′):

in which formulae (III) and (III′): R₇, R₈, R₉, R₁₀, R′₇, R′₈, R′₉ and R′₁₀, which may be identical or different, represent a hydrogen atom or a group chosen from: (C₁-C₆)alkyl; (C₁-C₆)alkoxy, (C₁-C₆)alkylthio; hydroxyl, mercapto; nitro, nitroso; R^(o)—C(X)—X′—, R^(o)—X′—C(X)—, R^(o)—X′—C(X)—X″— with R^(o) representing a hydrogen atom or a (C₁-C₆)alkyl or aryl group such as phenyl; X, X′ and X″, which may be identical or different, representing an oxygen or sulfur atom, or NR with R representing a hydrogen atom or a (C₁-C₆)alkyl group; (O)₂S(O⁻)—, M⁺ with M⁺ representing a hydrogen atom or a cationic counterion; (O)CO⁻—, M⁺ with M⁺ as defined previously; R″—S(O)₂—, with R″ representing a hydrogen atom, an alkyl group, or an aryl, (di)(C₁-C₆)(alkyl)amino or aryl(C₁-C₆)(alkyl)amino group; preferentially a phenylamino or phenyl group; R″′—S(O)₂—X′— with R″′ representing a (C₁-C₆)alkyl group or an aryl group which is optionally substituted, X′ as defined previously; (di)(C₁-C₆)(alkyl)amino; aryl(C₁-C₆)(alkyl)amino optionally substituted with one or more groups chosen from i) nitro; ii) nitroso; iii) (O)₂S(O⁻)—, M⁺ and iv) alkoxy with M⁺ as defined previously; optionally substituted heteroaryl; preferentially a benzothiazolyl group; cycloalkyl; notably cyclohexyl; Ar-N═N— with Ar representing an optionally substituted aryl group; preferentially a phenyl optionally substituted with one or more alkyl, (O)₂S(O⁻)—, M⁺ or phenylamino groups; or alternatively two contiguous groups R₇ with R₈ or R₈ with R₉ or R₉ with R₁₀ together form a fused benzo group A′; and R′₇ with R′₈ or R′₈ with R′₉ or R′₉ with R′₁₀ together form a fused benzo group B′; with A′ and B′ optionally substituted with one or more groups chosen from i) nitro; ii) nitroso; iii) (O)₂S(O⁻)—, M⁺; iv) hydroxyl; v) mercapto; vi) (di)(alkyl)amino; vii) R^(o)—C(X)—X′—; viii) R^(o)—X′—C(X)—; ix) R^(o)—X′—C(X)—X″—; x) Ar-N═N— and xi) optionally substituted aryl(C₁-C₆)(alkyl)amino; with M⁺, R^(o), X, X′, X″ and Ar as defined previously; W represents a sigma bond σ, an oxygen or sulfur atom, or a divalent radical i) —NR— with R as defined previously, or ii) methylene —C(R_(a))(R_(b))— with R_(a) and R_(b), which may be identical or different, representing a hydrogen atom or an aryl group, or alternatively R_(a) and R_(b) form, with the carbon atom that bears them, a spiro cycloalkyl; preferentially, W represents a sulfur atom or R_(a) and R_(b) together form a cyclohexyl; it being understood that formulae (III) and (III′) comprise at least one sulfonate radical (O)₂S(O⁻)—, M⁺ or one carboxylate radical (O)CO⁻—, M⁺ on one of the rings A, A′, B, B′ or C; preferentially sodium sulfonate; b) the pyrazolone anionic azo dyes of formulae (IV) and (IV′):

in which formulae (IV) and (IV′): R₁₁, R₁₂ and R₁₃, which may be identical or different, represent a hydrogen or halogen atom, a (C₁-C₆)alkyl group or —(O)₂S(O⁻)—, M⁺ with M⁺ as defined previously; R₁₄ represents a hydrogen atom, a (C₁-C₆)alkyl group or a —C(O)O⁻, M⁺ group with M⁺ as defined previously; R₁₅ represents a hydrogen atom; R₁₆ represents an oxo group, in which case R′₁₆ is absent, or alternatively R₁₅ with R₁₆ together form a double bond; R₁₇ and R₁₈, which may be identical or different, represent a hydrogen atom or a group chosen from: (O)₂S(O⁻)—, M⁺ with M⁺ as defined previously; Ar-O—S(O)₂— with Ar representing an optionally substituted aryl group, preferentially a phenyl optionally substituted with one or more alkyl groups; R₁₉ and R₂₀ together form either a double bond, or a benzo group D′, which is optionally substituted; R′₁₆, R′₁₉ and R′₂₀, which may be identical or different, represent a hydrogen atom or a (C₁-C₆)alkyl or hydroxyl group; R₂₁ represents a hydrogen atom or a (C₁-C₆)alkyl or (C₁-C₆)alkoxy group; R_(a) and R_(b), which may be identical or different, are as defined previously; preferentially, R_(a) represents a hydrogen atom and R_(b) represents an aryl group such as phenyl; Y represents either a hydroxyl group or an oxo group;

represents a single bond when Y is an oxo group; and represents a double bond when Y represents a hydroxyl group; it being understood that formulae (IV) and (IV′) comprise at least one sulfonate radical (O)₂S(O⁻)—, M⁺ or one carboxylate radical C(O)O⁻—, M⁺ on one of the rings D or E; preferentially sodium sulfonate; c) the anthraquinone dyes of formulae (V) and (V′):

in which formulae (V) and (V′): R₂₂, R₂₃, R₂₄, R₂₅, R₂₆ and R₂₇, which may be identical or different, represent a hydrogen or halogen atom, or a group chosen from: (C₁-C₆)alkyl; hydroxyl, mercapto; (C₁-C₆)alkoxy, (C₁-C₆)alkylthio; optionally substituted aryloxy or arylthio, preferentially substituted with one or more groups chosen from alkyl and (O)₂S(O⁻)—, M⁺ with M⁺ as defined previously; aryl(C₁-C₆)(alkyl)amino optionally substituted with one or more groups chosen from alkyl and (O)₂S(O⁻)—, M⁺ with M⁺ as defined previously; (di)(C₁-C₆)(alkyl)amino; (di)(hydroxy(C₁-C₆)alkyl)amino; (O)₂S(O⁻)—, M⁺ with M⁺ as defined previously; Z′ represents a hydrogen atom or a group NR₂₈R₂₉ with R₂₈ and R₂₉, which may be identical or different, representing a hydrogen atom or a group chosen from: (C₁-C₆)alkyl; polyhydroxy(C₁-C₆)alkyl such as hydroxyethyl; aryl optionally substituted with one or more groups, particularly i) (C₁-C₆)alkyl such as methyl, n-dodecyl, n-butyl; ii) (O)₂S(O⁻)—, M⁺ with M⁺ as defined previously; iii) R^(o)—C(X)—X′—, R^(o)—X′—C(X)—, R^(o)—X′—C(X)—X″— with R^(o), X, X′ and X″ as defined previously, preferentially R^(o) represents a (C₁-C₆)alkyl group; cycloalkyl; notably cyclohexyl; Z represents a group chosen from hydroxyl and NR′₂₈R′₂₉ with R′₂₈ and R′₂₉, which may be identical or different, representing the same atoms or groups as R₂₈ and R₂₉ as defined previously; it being understood that formulae (V) and (V′) comprise at least one sulfonate radical (O)₂S(O⁻)—, M⁺ or one carboxylate radical —C(O)O⁻, M⁺; preferentially sodium sulfonate; d) the nitro dyes of formulae (VI), (VI′) and (VI″):

in which formulae (VI) and (VI′): R₃₀, R₃₁ and R₃₂, which may be identical or different, represent a hydrogen or halogen atom, or a group chosen from: (C₁-C₆)alkyl; (C₁-C₆)alkoxy optionally substituted with one or more hydroxyl groups, (C₁-C₆)alkylthio optionally substituted with one or more hydroxyl groups; hydroxyl, mercapto; nitro, nitroso; polyhalo(C₁-C₆)alkyl; R^(o)—C(X)—X′—, R^(o)—X′—C(X)—, R^(o)—X′—C(X)—X″— with R^(o), X, X′ and X″ as defined previously; (O)₂S(O⁻)—, M⁺ with M⁺ as defined previously; (O)CO⁻—, M⁺ with M⁺ as defined previously; (di)(C₁-C₆)(alkyl)amino; (di)(hydroxy(C₁-C₆)alkyl)amino; heterocycloalkyl such as piperidino, piperazino or morpholino; in particular, R₃₀, R₃₁ and R₃₂ represent a hydrogen atom; R_(c) and R_(d), which may be identical or different, represent a hydrogen atom or a (C₁-C₆)alkyl group; W is as defined previously; W particularly represents an —N(H)— group; ALK represents a linear or branched divalent C₁-C₆ alkylene group; in particular, ALK represents a —CH₂—CH₂— group; n is 1 or 2; p represents an integer between 1 and 5 inclusive; q represents an integer between 1 and 4 inclusive; u is 0 or 1; when n is 1, J represents a nitro or nitroso group; particularly nitro; when n is 2, J represents an oxygen or sulfur atom, or a divalent radical —S(O)_(m)— with m representing an integer 1 or 2; preferentially, J represents an —SO₂— radical; M′ represents a hydrogen atom or a cationic counterion;

which may be present or absent, represents a benzo group optionally substituted with one or more groups R₃₀ as defined previously; it being understood that formulae (VI) and (VI′) comprise at least one sulfonate radical (O)₂S(O⁻)—, M⁺ or one carboxylate radical —C(O)O⁻, M⁺; preferentially sodium sulfonate; d) the triarylmethane dyes of formula (VII):

in which formula (VII): R₃₃, R₃₄, R₃₅ and R₃₆, which may be identical or different, represent a hydrogen atom or a group chosen from (C₁-C₆)alkyl, optionally substituted aryl and optionally substituted aryl(C₁-C₆)alkyl; particularly a (C₁-C₆)alkyl group and benzyl optionally substituted with an (O)_(m)S(O⁻)—, M⁺ group with M⁺ and m as defined previously; R₃₇, R₃₈, R₃₉, R₄₀, R₄₁, R₄₂, R₄₃ and R₄₄, which may be identical or different, represent a hydrogen atom or a group chosen from: (C₁-C₆)alkyl; (C₁-C₆)alkoxy, (C₁-C₆)alkylthio; (di)(C₁-C₆)(alkyl)amino; hydroxyl, mercapto; nitro, nitroso; R^(o)—C(X)—X′—, R^(o)—X′—C(X)—, R^(o)—X′—C(X)—X″— with R^(o) representing a hydrogen atom or an alkyl or aryl group; X, X′ and X″, which may be identical or different, representing an oxygen or sulfur atom, or NR with R representing a hydrogen atom or a (C₁-C₆)alkyl group; (O)₂S(O⁻)—, M⁺ with M⁺ representing a hydrogen atom or a cationic counterion; (O)CO⁻—, M⁺ with M⁺ as defined previously; or alternatively two contiguous groups R₄₁ with R₄₂ or R₄₂ with R₄₃ or R₄₃ with R₄₄ together form a fused benzo group optionally substituted with one or more groups chosen from i) nitro; ii) nitroso; iii) (O)₂S(O⁻)—, M⁺; iv) hydroxyl; v) mercapto; vi) (di)(C₁-C₆)(alkyl)amino; vii) R^(o)—C(X)—X′—; viii) R^(o)—X′—C(X)—; ix) R^(o)—X′—C(X)—X″—; with M⁺, R^(o), X, X′ and X″ as defined previously; particularly, R₃₇ to R₄₀ represent a hydrogen atom, and R₄₃ to R₄₄, which may be identical or different, represent a hydroxyl group or (O)₂S(O⁻)—, M⁺; and when R₄₃ with R₄₄ together form a benzo group, it is preferentially substituted with an (O)₂S(O⁻)— group; it being understood that at least one of the rings G, H, I or I′ comprises at least one sulfonate radical (O)₂S(O⁻)— or a carboxylate radical —C(O)O⁻; preferentially sulfonate; e) the xanthene-based dyes of formula (VIII):

in which formula (VIII): R₄₅, R₄₆, R₄₇ and R₄₈, which may be identical or different, represent a hydrogen or halogen atom; R₄₉, R₅₀, R₅₁ and R₅₂, which may be identical or different, represent a hydrogen or halogen atom, or a group chosen from: (C₁-C₆)alkyl; (C₁-C₆)alkoxy, (C₁-C₆)alkylthio; hydroxyl, mercapto; nitro, nitroso; (O)₂S(O⁻)—, M⁺ with M⁺ representing a hydrogen atom or a cationic counterion; (O)CO⁻—, M⁺ with M⁺ as defined previously; G represents an oxygen or sulfur atom or a group NR_(e) with R_(e) as defined previously; particularly, G represents an oxygen atom; L represents an alkoxide O⁻, M⁺; a thioalkoxide S⁻, M⁺ or a group NR_(f), with R_(f) representing a hydrogen atom or a (C₁-C₆)alkyl group, and M⁺ as defined previously; M⁺ is particularly sodium or potassium; L′ represents an oxygen or sulfur atom or an ammonium group: N⁺R_(f)R_(g), with R_(f) and R_(g), which may be identical or different, representing a hydrogen atom, a (C₁-C₆)alkyl group or an optionally substituted aryl group; L′ represents particularly an oxygen atom or a phenylamino group optionally substituted with one or more alkyl or (O)_(m)S(O⁻)—, M⁺ groups with m and M⁺ as defined previously; Q and Q′, which may be identical or different, represent an oxygen or sulfur atom; particularly Q and Q′ represent an oxygen atom; M⁺ is as defined previously; f) the indole-based dyes of formula (IX):

in which formula (IX): R₅₃, R₅₄, R₅₅, R₅₆, R₅₇, R₅₈, R₅₉ and R₆₀, which may be identical or different, represent a hydrogen atom or a group chosen from: (C₁-C₆)alkyl; (C₁-C₆)alkoxy, (C₁-C₆)alkylthio; hydroxyl, mercapto; nitro, nitroso; R^(o)—C(X)—X′—, R^(o)—X′—C(X)—, R^(o)—X′—C(X)—X″— with R^(o) representing a hydrogen atom or an alkyl or aryl group; X, X′ and X″, which may be identical or different, representing an oxygen or sulfur atom, or NR with R representing a hydrogen atom or a (C₁-C₆)alkyl group; (O)₂S(O⁻)—, M⁺ with M⁺ representing a hydrogen atom or a cationic counterion; (O)CO⁻—, M⁺ with M⁺ as defined previously; G represents an oxygen or sulfur atom or a group NR_(e) with R_(e) as defined previously; particularly, G represents an oxygen atom; R_(i) and R_(h), which may be identical or different, represent a hydrogen atom or a (C₁-C₆)alkyl group; it being understood that formula (IX) comprises at least one sulfonate radical (O)₂S(O⁻)—, M⁺ or one carboxylate radical —C(O)O⁻, M⁺; preferentially sodium sulfonate; g) the quinoline-based dyes of formula (X):

in which formula (X): R₆₁ represents a hydrogen or halogen atom or a (C₁-C₆)alkyl group; R₆₂, R₆₃ and R₆₄, which may be identical or different, represent a hydrogen atom or a group (O)₂S(O−)—, M+ with M+ representing a hydrogen atom or a cationic counterion; or alternatively R₆₁ with R₆₂, or R₆₁ with R₆₄, together form a benzo group optionally substituted with one or more groups (O)₂S(O⁻)—, M⁺ with M⁺ representing a hydrogen atom or a cationic counterion; it being understood that formula (X) comprises at least one sulfonate radical (O)₂S(O⁻)—, M⁺ preferentially sodium sulfonate; more particularly, the anionic dye(s) are chosen from the dyes of formula (V) such as Acid Violet
 43. 6. The process as claimed in any one of the preceding claims, in which the salt(s) of formula (A) are such that R₁ represents a linear or branched, preferably linear, saturated or unsaturated (C₁-C₁₀) hydrocarbon-based group, optionally substituted with one or more groups chosen from hydroxyl, (C₁-C₄)alkoxy, —SO₃H, —SO₃ ⁻ and phenyl; preferentially, R₁ represents a linear or branched, more preferentially linear, (C₁-C₈)alkyl group, optionally substituted with one or more hydroxyl, phenyl, —SO₃H and —SO₃ ⁻ groups, or alternatively R₁ represents a linear or branched (C₂-C₆)alkenyl group, preferably vinyl or allyl.
 7. The process as claimed in any one of the preceding claims, in which the salt(s) of formula (A) are such that Y′ represents an anionic counterion chosen from i) halides such as chloride, bromide, ii) hydrogen sulfates, iii) (bis)(poly)halo(C₁-C₁₂)(alkyl)sulfonylimides such as bis(trifluoromethylsulfonyl)imide and bis(fluorosulfonyl)imide, iv) (C₁-C₁₂)alkyl sulfates, v) (poly)halophosphates such as hexafluorophosphate, vi) (C₁-C₁₂)(alkyl)phosphates such as phosphate, vii) (poly)haloborates such as tetrafluoroborate, viii) carbonate, ix) bicarbonate, x) (C₁-C₁₂)alkylcarbonates, xi) dicyanamide, xii) nitrate, xiii) thiocyanate, xiv) formate, xv) (C₁-C₁₂)alkylcarboxylates in which the (C₁-C₁₂)alkyl group may be substituted with one or more halogen atoms or groups chosen from hydroxyl, (C₁-C₆)(di)(alkyl)amino, phenyl, imidazole, (C₁-C₄)alkylcarbonyl, (C₁-C₄)alkylcarbonyloxy, (C₁-C₄)alkylcarbonylamino, guanidine, thiol, —SO₃H, (C₁-C₈)alkoxy such as trifluoroacetate; xvi) (C₆-C₁₂)arylcarboxylates in which the aryl group may be substituted with one or more halogen atoms or groups chosen from hydroxyl, (C₁-C₆)(di)(alkyl)amino, phenyl, imidazole, (C₁-C₄)alkylcarbonyl, (C₁-C₄)alkylcarbonyloxy, (C₁-C₄)alkylcarbonylamino, guanidine, thiol, —SO₃H, (C₁-C₈)alkoxy; xvii) (C₁-C₁₂)alkylsulfonates in which the (C₁-C₁₂)alkyl group may be substituted with one or more halogen atoms or groups chosen from hydroxyl, (C₁-C₆)(di)(alkyl)amino, phenyl, imidazole, (C₁-C₄)alkylcarbonyl, (C₁-C₄)alkylcarbonyloxy, (C₁-C₄)alkylcarbonylamino, guanidine, thiol, —SO₃H, (C₁-C₈)alkoxy such as triflate, in particular (C₁-C₆)alkylsulfonates such as methylsulfonate or mesylate; and xviii) (C₆-C₁₂)arylsulfonates in which the aryl group may be substituted with one or more halogen atoms or groups chosen from hydroxyl, (C₁-C₆)(di)(alkyl)amino, phenyl, imidazole, (C₁-C₄)alkylcarbonyl, (C₁-C₄)alkylcarbonyloxy, (C₁-C₄)alkylcarbonylamino, guanidine, thiol, —SO₃H, (C₁-C₈)alkoxy such as benzenesulfonate and toluenesulfonate ortosylate; preferentially, Y⁻ represents

more preferentially, Y⁻ is chosen from i), xvii) and xviii); more preferentially, Y⁻ is chosen from chloride, bromide, methyl sulfate and tosylate.
 8. The process as claimed in any one of the preceding claims, in which the salt(s) of formula (A) are chosen from those of formulae (I) and (II) below, and also the tautomeric forms thereof:

in which formulae (I) and (II): R₁ represents a linear or branched, saturated or unsaturated (C₁-C₁₂) hydrocarbon-based group optionally substituted with one or more groups chosen from hydroxyl, amino, (C₁-C₆)dialkylamino, (C₁-C₆)alkylamino, carboxyl, carboxylate, carbamide, (C₁-C₄)alkoxy, —SO₃H, sulfonate and phenyl; R′₁ represents a hydrogen atom, a linear or branched, saturated or unsaturated (C₁-C₁₂) hydrocarbon-based group optionally substituted with one or more groups chosen from hydroxyl, amino, (C₁-C₆)dialkylamino, (C₁-C₆)alkylamino, carboxyl, carboxylate, carbamide, (C₁-C₄)alkoxy, —SO₃H, sulfonate and phenyl; and R₂ represents a hydroxyl group, a linear or branched, saturated or unsaturated (C₁-C₁₂) hydrocarbon-based group optionally substituted with one or more groups chosen from hydroxyl, (C₁-C₄)alkoxy, —SO₃H, sulfonate and benzene; n is 0, 1, 2 or 3; preferably, n is 0 or 1; Y⁻ represents an anionic counterion; it being understood that: when one of the hydrocarbon-based groups of R₁, R′₁ or R₂ is substituted with a carboxylate or sulfonate group, then Y⁻ is absent to ensure the electrical neutrality of the salt of formula (A), and when n is equal to 2 or 3, then the substituents are identical or different.
 9. The process as claimed in claim 8, in which the salt(s) of formula (I) are such that R′₁ represents a hydrogen atom or a linear or branched, saturated or unsaturated (C₁-C₈) hydrocarbon-based group optionally substituted with one or more groups chosen from hydroxyl, (C₁-C₂)alkoxy, —SO₃H, —SO₃ ⁻ and phenyl; preferentially, R′₁ represents a hydrogen atom or a saturated, linear or branched, more preferentially linear, (C₁-C₆) hydrocarbon-based group, particularly methyl.
 10. The process as claimed in claim 8 or 9, in which the salt(s) of formula (I) are such that R₂ represents a linear or branched, saturated (C₁-C₆) hydrocarbon-based group such as methyl; preferably, n is 1 and R₂ is in position
 2. 11. The process as claimed in claim 8, in which the salt(s) of formula (II) are such that R₁ represents a linear or branched, saturated or unsaturated (C₁-C₁₂) hydrocarbon-based group; in particular, R₁ represents a linear or branched (C₁-C₈)alkyl group, preferably R₁ represents a (C₁-C₄)alkyl group such as methyl.
 12. The process as claimed in claim 8 or 11, in which the salt(s) of formula (II) are such that R₂ represents a hydroxyl group, a linear or branched, saturated or unsaturated (C₁-C₁₂) hydrocarbon-based group, optionally substituted with one or more hydroxyl, (C₁-C₄)alkoxy, —SO₃H, —SO₃ ⁻ and phenyl groups; preferentially, R₂ represents a hydroxyl group or a (C₁-C₄)alkyl group such as methyl; R₂ is preferably positioned in position 2′, 3′ or 4′.
 13. The process as claimed in any one of claims 1 to 7, in which the salt(s) of formula (A) are chosen from compounds 1 to 40:

preferably 2, 3, 4, 5, 34 and 36, more preferentially 2, 4, 5 and
 36. 14. The process as claimed in any one of the preceding claims, which comprises the step of applying to said fibers a composition, preferably an aqueous composition, comprising a) one or more direct dyes as defined in any one of claims 1 to 5 and b) one or more unsaturated heterocycles (A), (I) or (II) as defined in any one of claims 6 to
 13. 15. The process as claimed in any one of claims 1 to 13, which comprises: either i) a first step of applying to said materials a composition, preferably an aqueous composition, comprising a) one or more direct dyes as defined in any one of claims 1 to 5 and then ii) a step of applying to said materials a composition, preferably an aqueous composition, comprising b) one or more unsaturated heterocyclic salts of formula (A), (I) or (II) as defined in any one of claims 6 to 13; or i) a first step of applying to said materials a composition, preferably an aqueous composition, comprising b) one or more unsaturated heterocyclic salts of formula (A), (I) or (II) as defined in any one of claims 6 to 13 and then ii) a step of applying to said materials a composition, preferably an aqueous composition, comprising a) one or more direct dyes as defined in any one of claims 1 to
 5. 16. The process as claimed in either of claims 14 and 15, in which a) the direct dye(s) as defined in any one of claims 1 to 5 represent from 0.001% to 10% by weight, preferentially from 0.05% to 5% by weight relative to the total weight of the composition comprising them, more preferentially from 0.3% to 3% by weight relative to the total weight of the composition comprising them.
 17. The process as claimed in any one of the preceding claims, in which a) the direct dye(s) have a solubility in water at a temperature of 22° C. and at atmospheric pressure (760 mmHg, i.e. 1.013×10⁵ Pa) of less than 5% by weight, preferably less than 1% by weight and more preferentially less than 0.5% by weight.
 18. The process as claimed in any one of claims 14 to 17, in which b) the heterocyclic salt(s) (A), (I) or (II) as defined in any one of claims 6 to 13 are present in amounts ranging from 1% to 99.5% by weight, preferably from 3% to 90% by weight, more preferentially from 10% to 90% by weight, better still from 20% to 80% by weight, even more preferentially from 30% to 70% by weight and most preferentially from 40% to 60% by weight relative to the total weight of the composition comprising them.
 19. The process as claimed in any one of claims 14 to 18, in which the pH of the composition(s) comprising ingredients a) and b) is between 3 and 13, preferably between 5 and 10 and more preferentially between 6 and 9.5.
 20. The composition as defined in any one of claims 14 and 16 to 19, comprising a) one or more direct dyes as defined in any one of claims 1 to 5 and b) one or more unsaturated heterocycles (A), (I) or (II) as defined in any one of claims 6 to
 13. 21. A multi-compartment device or kit, comprising at least a first compartment which contains at least one direct dye as defined in any one of claims 1 to 5, and at least a second compartment which contains at least one heterocyclic salt of formula (A), (I) or (II) as defined in any one of claims 6 to
 13. 